Apparently had an unscrupulous past, but no details have been given
Sentenced to community service for punching out some cops who tried to intervene in a fight with Robert 
Charged with attempted murder when he sneaked into Robert's room with a concealed knife; later cleared after the weapons used against Robert are found in Mac's old shipmate's foot locker 
Borrowed money from a loan shark who worked for Joseph Sorel, in order to pay off his excessive gambling debts
Blew up a mine owned by the Jacks family while working for them, causing severe injuries to Miranda Jacks (then wife of Jasper Jacks)
Beat up Lucky Spencer after he learned of Lucky's adulterous affair with Maxie [Sep 2006]
Mac arrived in Port Charles on Valentine's Day in 1991, on a ship owned by the Quartermaines, called the S.S. Tracy. The ship was having trouble docking into the Port Charles harbor due to engine problems as well as protesters causing a scene. When the ship caught on fire after an explosion, Mac jumped into the water. He was dragged out by Police Commissioner, Robert Scorpio, Mac's older brother. The pair came face to face after many years of estrangement. Robert was very hostile to Mac and called him a killer as well as accusing him of having something to do with the ship's engine problems. Mac's problems with Robert got worse when several attempts on Robert's life were made. Robert accused Mac of being behind the death threats. When Robert was critically wounded after someone threw a plastic explosive into his office, Mac was labeled the prime suspect. When Mac went to see his brother in I.C.U. Robert's lover, Anna knocked him down to stop him from going in Robert's room. Anna found a knife in Mac's boot and assumed he came there to do his brother harm. Mac was arrested and charged with attempted murder. He hired Scott Baldwin to represent him. It was later learned that the brothers' estrangement was due to the fact that Mac and Robert's parents and Robert's fiancée, Lily, were killed in a plane crash. Mac was supposedly being careless and showing off to impress their father with his piloting skills when their plane crashed. Mac went to get help for a seriously injured Robert, but Robert assumed Mac had left to save himself. Robert was rescued by someone else and Mac returned to find no trace of Robert.
Mac managed to escape from jail when an earthquake hit Port Charles. Robert found Mac trying to leave town on the next ship heading out of Port Charles. They had a fight in which Robert knocked Mac overboard. Mac was later presumed dead when no body was found and there wasn't any appearance of Mac in the water. Robert was guilt ridden, thinking he killed his brother. Later, Robert was lead into a trap. He came face to face with Mac in the Finger Lakes area of New York. They eventually came to the conclusion that they were set up by someone who hired Mac to come to town. Robert was shot and Mac helped him get to a community clinic for medical attention. Mac donated blood to help give Robert a needed transfusion after losing a lot of blood. They patched up their differences and explained what happened to each other when they lost their parents in the crash. Robert convinced Mac to head back to Port Charles and clear his name. Mac confessed his crimes to Robert and revealed the name of the person who had hired him. Anna managed to find the brothers after they had escaped from the county jail. The trio hid out in a mansion in Finger Lakes from the local sheriff who didn't believe Robert and Mac's story regarding the death of Rory. The woman who lived there, Dominique Taub, invited them to stay and took a shine to Mac right away. Dominique turned out to be deaf and very married. Mac still was very attracted to her and eventually hid her in Port Charles from her abusive husband.
Back in Port Charles, Mac opened a new club called the Outback. Dominique's childhood nanny, who had only recently arrived, was murdered opening night. Dom was charged with her nanny's murder and her husband managed to obtain legal guardianship of her. Mac got beat up trying to help Dom escape and Dom's husband carted her off to make an heir. Dom escaped back to PC only to be hit by a car and found once again by her husband. So Mac helped her stage her suicide and made plans to flee the country with her. While in hiding, Dom refused to make love with Mac due to flashbacks of the abuse she suffered at the hands of her husband. Caught once again by her husband, Dom was put into a sanitarium where Mac secretly visited her. Her therapist informed them that Dom would need lots of therapy before she would be capable of a real relationship with Mac. While Dom worked on getting better, Mac helped Robert and Anna in their fight against the Cartel. Mac, Robert, Anna, and Bill finally defeated the Cartel and the members were sent to prison. Dominique was finally free to be with Mac after her husband, a member of the Cartel, was killed while escaping from prison. Mac taught her that a man can be gentle and kind and they fell in love. Mac's relationship with Dominique became strained later, however, when Mac was informed his brother Robert was killed in a boat explosion after trying to save his wife Anna. Mac had agreed to take care of his niece, Robin when Robert had left to find Anna. Now Mac was Robin's guardian and all his time with her didn't allow him to focus on Dominique very much. Mac broke up with Dominique when he realized he couldn't love her the way she wanted him to.
Mac found himself using his skills as a P.I. when Felicia Jones returned to town under mysterious circumstances suffering from amnesia. He hired her as a bartender at the Outback and helped her unravel the mystery behind her nightmares of witnessing a murder. Mac admitted to having feelings for Felicia and they started dating. When Felicia remembered that she had seen Ryan Chamberlain kill a woman in Texas, she stabbed Ryan in a struggle and Mac found her standing over his unconscious body. Felicia was charged with attempted murder and sentenced to a term in a mental hospital. Mac rescued her and they went on the run from the law. They began digging into Ryan's past and faked Felicia's death to throw Ryan off their trail. After discovering that Ryan had committed several murders, they tried to get Ryan to confess to them on tape. Eventually Ryan was apprehended and convicted of murder.
Mac and Felicia became closer than ever and tried to fight off their attraction to no avail. They agreed to go slowly and date. Mac fell in love with her and asked her to marry him in the middle of trying to catch an escaped Ryan. She said no at first due to her failed relationship with Frisco. But after nearly being killed by Ryan, Felicia realized she loved Mac and proposed to him. He said yes and they celebrated by making love for the first time. While they planned their wedding, they became partners in a private investigation business. Their wedding was ruined when Ryan escaped from the mental hospital and assumed his twin brother Kevin's identity. He went to the church with a bomb and Mac struggled with him to get it away from him. Mac was injured and they had to postpone their wedding. However, their wedding never happened. Felicia's young daughter Maxie was very sick and needed a heart transplant. Mac found Maxie's father Frisco in Africa and convinced him to return to PC in case his daughter died. Mac saw that Felicia still had unresolved feelings for Frisco. Mac broke up with her but the two remained best friends. Mac was upset when Felicia informed him she was pregnant with Frisco's baby, not his. However, Mac accepted Georgie instantly and loved both her daughters like a father. Mac became romantically involved with Katherine Bell, who was very different from Mac in many ways. They nearly broke up months later when Lucy informed Mac and Damian that Katherine had been seeing both of them. Lucy was retaliating for Kevin and Mac dressing in drag in order to prove Madame Maia, Lucy's psychic, was a fake. But Katherine sweet-talked Mac into giving her another chance.
Mac and Robin began butting heads over her new flame, Stone Cates. Mac wasn't pleased that Stone lived with local mobster Sonny Corinthos. After Robin gloated to Mac about sleeping with Stone despite his attempts to prevent it, Felicia suggested Robin should go on the Pill. Then Robin slept with Stone without using a condom. When Stone complained of severe headaches and a cold that wouldn't go away, Kevin ordered blood tests. The tests revealed that Stone was HIV positive. Stone couldn't bring himself to tell Robin until he got shot and she attempted to help him. At the hospital, Alan persuaded Robin to be tested as well but she was negative. Alan also told Stone he had advanced AIDS and started him on drug therapy immediately. Afraid of infecting her, Stone refused to sleep with Robin anymore. When Robin finally told Mac that Stone had AIDS and that they had unprotected sex, Mac was very angry and scared. But he eventually warmed up to Stone. When Mac threw Robin a surprise party, the guests presented Stone with the memory book she had initiated. In the book were several letters written by Stone's friends, including a touching one from Mac. As Stone's health failed, Alan discovered that he had lymphoma. Stone chose to forego treatment and his friends rallied around him during his last few weeks of life. Near the end, Stone made Robin get tested again. This time the test revealed Robin to be HIV positive. Mac was very loving and supportive of her. But Stone was devastated and screamed out in frustration. Mac and Sonny took turns watching over the ailing couple and Stone quietly died within a few days. His memorial service was held at Sonny's penthouse. At the annual Nurses Ball, Mac had an AIDS Memorial Quilt made in Stone's memory.
Mac used Katherine as an informant against Damian and later helped to clear her of Damian's murder. Convinced that Damian was alive, Mac, Luke, and Kevin headed to Texas to find him. Later Damian was killed in the fire at the Ward House. Katherine was not happy when Mac began spending more time with Felicia in the aftermath of Felicia's stalking by Kevin. Things got worse between the pair when Jax's first wife Miranda showed up in town. Miranda and Mac had lived together in Australia. Working for the Jacks family, Mac had set off an explosion and thought she had died in it. Mac proposed to Katherine but she turned him down. Felicia comforted Mac as a friend and they grew close as they went through several different adventures.
Mac had a hard time accepting Robin's next boyfriend, Jason Morgan. Jason also worked for Sonny Corinthos. Robin eventually went away to school. Mac became the Police Commissioner after seeing police corruption get out of hand. He also found himself involved in a case with his best friend, Felicia. Felicia took on a case of a woman named Tess who hired her to find her missing husband, who left her years ago. Felicia noticed the man looked identical to Mac in the picture Tess showed her. Mac was later kidnapped by Tess but managed to escape and find out what Tess' plan was for him. He was being set up to take the fall for the assassination of his old foe, Jasper Jacks. Tess was apprehended. Mac and Felicia, however, had their own predicament. Felicia had accepted a marriage proposal from the fake Mac, James Meadows. All of their friends were so happy for them that they couldn't tell them the engagement was a lie. They eventually found themselves in love with each other after having to pretend they were engaged. Mac professed his love to Felicia at the altar of their double wedding with Lucy and Kevin. They had planned on calling off their wedding and telling their friends the truth. Instead, Lucy and Kevin called off their wedding and Mac and Felicia got hitched. Felicia shared the whole story involving Tess, James, and the fake engagement with the congregation before exchanging vows from the heart with Mac. They celebrated with their family and then flew off to Paris for their honeymoon.
Their marriage was happy for the first year or so. Mac was wounded in a shoot-out at the Outback but later recovered. Felicia began writing Lila Quartermaine's memoirs and enlisted Luke Spencer, who was grieving over his son's death, to help her. Mac trusted Felicia when she was working with Luke on her book, but after he rescued them from being locked together in a crypt, he warned Luke to stay away from his wife. However, Felicia continued to work with Luke and lied to Mac about it.
Mac also had to deal with the return of his brother's enemy, Cesar Faison, who was very much alive after all. Cesar wanted revenge on Mac. After months of taunting Mac by approaching his loved ones, Faison kidnapped Felicia. Both Luke and Mac went looking for her. Luke managed to find her first, but ended up becoming a captive as well. Trapped together, Felicia and Luke nearly made love but stopped before anything actually happened. However, they didn't realize that Faison had taped their encounter. Mac soon rescued them, but the duo remained mum about what had nearly happened. Faison later sent the tape to Mac at Christmas time in 1999. Mac was devastated by the video. He eventually confronted Felicia with the video and left her. He forgave her and the two agreed to try to save their marriage.
Mac took another blow when Felicia went back on her promise to stay away from Luke and left town to help him find his son. Mac was fed up and filed divorce papers as well as custody papers for custody of Maxie and Georgie. He later dropped the custody battle and proceeded with just the divorce. Mac found himself also letting his bias interfere with his job. He railroaded Luke into a murder charge knowing the evidence was very circumstantial at best. Mac also missed Felicia terribly while she went on vacation with her girls. He agreed to give their marriage a chance after all when Felicia told him she loved him still. However, it didn't last. Felicia took the stand when it looked like Luke could be found guilty of murdering Stefan. Felicia testified that she was in a motel with Luke and made love to him the night of Stefan's "murder." Mac was devastated. He was also humiliated when Stefan showed up alive and well in PC. Mac resigned as Police Commissioner and went back to private investigating.
After realizing that he still loved Felicia, he vowed to her that he would win her back from Luke. But he soon realized that she was in love with Luke by then. Felicia tried to have a deeper relationship with Luke, but Luke was too wrapped up in other things to notice. Heartbroken, Felicia took the girls to Texas with her for awhile. Mac found himself returning to his police commissioner job again in the midst of the investigation into Sorel's murder. There were several suspects in the murder of Joseph Sorel, several of whom stepped forward to try to implicate someone else. As the case developed several twists and turns, Mac asked Felicia to help him figure out the identity of the murderer. After gathering all the suspects in an old mansion and eliminating them one by one, Mac and Felicia figured out that Sorel's daughter Angel had killed Sorel. They went to arrest her at her lake house, but Jax, Sonny, Carly, and Angel had arranged for Carly and Angel to switch places to fool the cops. By the time Mac got to the house, Jax had already gotten Angel onto a plane headed out of the country.
As the Spencer/Cassadine war came to a boiling point, Gia tried to get Mac to arrest Stavros/Lucien Cane. He refused since she had recently cried wolf on several occasions. But when Helena and Stavros were finally defeated in her underground lab, Mac was right there to arrest Helena. To everyone's dismay, Mac wasn't able to find any physical evidence of Helena's latest evil actions, including bringing Stavros back to life. When Helena doubled over in pain in her cell during a visit from Luke, Mac tried to convince him that she really was sick and was scheduled for surgery. He warned Luke to stay away from her. Helena later escaped, and Mac butted heads with Luke on how to handle looking for her. Luke caught Helena and brought her back to the cops. Mac even allowed Luke to accompany Helena to the prison van to make sure she didn't escape again.
Mac tried to look out for Felicia by warning her against a relationship with Roy DiLucca, who had recently made moves towards becoming a mobster. She asked Mac to help her trace a briefcase full of cash that had shown up in Roy's apartment. She also told Mac that she could handle things with Roy.
As Luke and Laura prepared for their upcoming wedding, Laura began having flashbacks of a night long ago in the garage attic of her childhood home, which belonged to the Scorpios now. When a fire broke out in the garage attic while Maxie was watching Lulu, Mac yelled at Maxie for putting Lulu in danger. He discovered that the fire had been deliberately set. Luke wanted Mac to ask Scott what he knew about it. Luke claimed Scott had been acting weird and wondered why Scott had been the first on the scene. But Mac had no evidence to validate Luke's suspicions. Luke continued to look into the incident of long ago. When Rick Webber, Laura's stepfather, turned up dead due to a drunk-driving accident, Mac and Scott knew right away that it was a set up. Although they believed Lucky and Nikolas were responsible for moving the body, they thought Luke had actually killed Rick in the attic. When Luke and Laura returned to the attic a few weeks later, Mac arrested Luke and Scott had Laura admitted to the hospital for mental evaluation.
Mac had a murder to investigate when Luis Alcazar was thrown from his hotel balcony. Alcazar, an international arms dealer, had come to town a few months earlier with Brenda, who hadn't perished in the car crash years earlier. Alcazar wanted to eliminate Brenda's past loves, Sonny and Jax, so that he could have her for himself. But she refused to be with him and resumed a relationship with Jax. After crashing her surprise party at the Quartermaines, Alcazar had left before Mac arrested him for trespassing and was later killed. Mac arrested Jason after AJ claimed to have seen Jason driving Alcazar's limo that night. Then Skye claimed to have seen Brenda actually push Alcazar off the balcony. As Mac took Skye's statement about seeing Brenda kill Alcazar, he realized that she was drunk at the time and wanted to get back at Brenda for stealing Jax away from her. Scott was also desperate to pin the murder on any associate of Sonny's. He planted a bug in the interrogation room, but Mac found it and took it out. Mac then told Scott that he wouldn't tolerate Scott's illegal antics in solving Alcazar's murder. Mac tried to help solve the case by re-enacting the events of that evening to get Brenda to remember more and to disprove Jax's recent confession. But no new leads emerged and Mac went to arrest Brenda at the Quartermaine holiday party. However, Brenda and Jax eluded Mac when the lights went out and the Quartermaines refused to point him in the right direction. Felicia later persuaded Mac to give her the location of the witness Scott had found that stated she had seen Brenda kill Alcazar. Since Mac believed in Brenda's innocence, he agreed to help Felicia, who was working to clear Brenda and Jason of the murder. Brenda and Jason were later cleared by the real killer, who turned out to be Alexis Davis.
When Felicia went to Texas to take care of her ailing grandmother Maria, Mac became the primary parent in Maxie and Georgie's lives. Mac had his hands full with Maxie. She acted the typical part of rebellious teenager by going to parties and drinking. Mac managed to break up the party Maxie tried to throw at their house and announced that he was moving in to keep a better eye on them. When Maxie went to a party and slept with Kyle, one of the popular guys at school, she didn't realize that their encounter was being broadcasted over the Internet. Mac found out about it when he was investigating a tip about a porn site featuring PC high school kids. He saw red when he realized that he was watching Maxie. But when Mac confronted Maxie and demanded to know who the boy in the film was, she wouldn't tell him. After Maxie nearly died of a drug overdose, Mac blamed Jason and Sonny for the recent influx of drugs in Port Charles. After Jason convinced him that they weren't responsible, Mac told Jason he'd be willing to look the other way if Jason wanted to kill the responsible party.
Soon Georgie was giving Mac headaches as well by dating Dillon Quartermaine. Fed up with the lack of warmth from his family, Dillon wanted to run away and convinced Georgie to join him. When Mac found out that Georgie was gone, he tracked the pair to a motel and barged in the room to find them kissing. Livid, Mac arrested Dillon but later released him. However, he warned the pair to stay away from each other. After Dillon found himself stuck with his job for mobster Lorenzo Alcazar, Georgie convinced him to tell all to Mac in an attempt to prove his worthiness to date Georgie. Instead, Mac told Dillon his recent partnership with Alcazar was a good reason for him to stay away from Georgie. When he caught Dillon the next morning in Georgie's room he threw him out and then attempted to warn Georgie of the dangers of having sex. She assured him that she wasn't sleeping with Dillon. When Georgie rented a room a few weeks later at the Port Charles Hotel in order to have a romantic evening of love making with Dillon, Mac interrupted and had a heart to heart with Georgie. He told her that he only wanted what was best for her. Shaken by Mac's loving words, Georgie postponed her night of passion with Dillon.
While dealing with his kids, Mac silently kept the criminal element in line in Port Charles. He investigated Carly's kidnapping by Ric Lansing and then Ric's disappearance. When a raid on a drug shipment went sour, a shootout between the cops and the mob ensued. One of the cops was shot and Faith later named Zander as the shooter. Desperate, Zander went on the run. Mac didn't realize that Maxie was hiding Zander in her room. Maxie managed to get Zander to the basement of the PC Hotel and promised to get the cash he needed to flee the country. However, Nicolas found Zander first, knocked him out, and called the cops to come arrest him. Mac went to arrest Zander with another officer. Unaware that a fire had broken out in the electrical room where Zander was hiding, Mac opened the door. He was caught in a back draft and suffered severe burns. When Maxie found out what had happened to Mac, she went to his bedside to be with him and confessed that she had been hiding Zander. When Georgie was finally rescued from the fire and arrived at the hospital, Maxie tearfully informed her of Mac's condition. Dillon supported Georgie as she went to see a badly burned Mac. The sisters continued to worry as Mac's condition seemed to worsen. Tracy Quartermaine kept lurking around, spouting false sympathies in the hopes that the girls wouldn't hold the Quartermaines, who owned the hotel, responsible for Mac's condition. Georgie finally told Tracy off.
Felicia returned while Mac was hospitalized to resume her role of mother. She supported her daughters in their grief over Mac and sat by Mac's beside. She urged him to get better. Later Felicia learned that Mac had disappeared from the hospital. She found him at Mercy Hospital labeled with a John Doe name tag. She vowed to unravel the mystery of his transfer. When Mac awoke, he asked Felicia to just let this mystery go and focus on her family. But Felicia still wondered what had happened.
Mac made a full recovery and returned to his work as the police commissioner. He also resumed his worry over Maxie and Georgie growing up. Mac was less than pleased to learn of Maxie's involvement in solving a murder case with her boyfriend, police officer Jesse Beaudry. Mac forbade Maxie to interfere ever again in police investigations, which she blatantly ignored when she conducted her own investigation into who was giving young women the date rape drug and photographing them nude. Mac also worried about Georige and remained distrustful of her relationship with Dillon, especially after Dillon was a possible suspect in the campus stalker case. Mac was relieved to learn Dillon was innocent but his fear for Georgie returned when the real stalker, Diego Alcazar, took Georgie hostage but released her unharmed.
In February of 2006, Dillon contracted a potentially deadly form of encephalitis and he and Georgie decided they wanted to marry before he died. Since Georgie was not yet legally an adult, Mac's consent was required for the marriage. He initially refused her request but she convinced him to change his mind. He attended the intimate ceremony which took place in Dillon's hospital room. Dillon survived but the marriage between Dillon and Georgie ended.
Around the same time, Maxie struggled to cope with the death of her boyfriend Jesse and turned to his former partner, Lucky Spencer, for comfort. Lucky was married to Elizabeth but Maxie lured Lucky into an affair by feeding his addiction to prescription painkillers. When Lucky ended his relationship with Maxie, she attempted suicide and told Mac about her involvement with Lucky and his drug use. Mac paid a visit to Lucky and beat him up. Mac continued to blame Lucky for causing Maxie pain after Maxie claimed to have miscarried Lucky's child after she fell down a flight of stairs during an argument with him.
Mac was placed in a difficult predicament in 2007 when the Metro Court was taken hostage by a man named James Craig. Both Robin and Maxie were trapped inside as hostages, yet Mac had to remain calm and under control in his role as police commissioner. It was especially difficult after he learned that Robin had been shot but he was unable to negotiate her release. The hostage crisis ended in an explosion and Mac was relieved to learn that Maxie and Robin had made it out. Maxie was unharmed and Robin required a surgery to repair the damage from the gunshot.
Mac continued to be concerned with the safety of his girls when a text message killer was on the loose. Georgie and her new computer genius friend Damian Spinelli suspected Maxie's police officer boyfriend Cooper Barrett was the killer and rushed to warn Maxie. Georgie arrived just in time to thwart the killer's attack on Maxie. Mac was horrified to learn of Maxie's brush with death but it was nothing compared to the reality of the pain
Mac experienced when he learned Georgie's life had been taken by the killer who was later revealed to be Diego Alcazar. After the tragedy of Georgie's death, the Scorpio family received some good news when Robin shared she was pregnant. Robin and the child's father, Patrick Drake, were in love with one another but they struggled with sorting out their feelings for one another. Mac repeatedly warned Patrick that he was not good enough for Robin but in the end he supported their decision to marry. He agreed to walk Robin down the aisle in place of her father, but Robin went into labor at the start of the ceremony. She gave birth to a daughter named Emma and Mac was a proud and protective great uncle. A few weeks after Emma arrived, Patrick and Robin wed with both of Robin's parents present and Mac agreed that Robert should be the one to escort Robin down the aisle.
Maxie was next to take a walk down the aisle when she accepted Spinelli's proposal, against Mac's wishes. He expressed repeatedly that he believed Maxie was too young to be married and that he did not want her living off of mob money, since Spinelli was employed by Jason Morgan. Mac often threatened to arrest Spinelli in order to stop the wedding, but on the day of the ceremony, he gave Maxie his support. To his relief, Spinelli realized Maxie was not ready to be married and he called off the wedding. The non-married couple hosted a reception at Jake's and Mac celebrated heartily.
Although Robin and Maxie were each involved in romantic relationships of their own, they joined Molly and Kristina Davis in their plan to foster a romance between Alexis Davis and Mac. Alexis was hesitant to join Mac on a date but she succumbed to the pressure from her daughters and joined Mac at Jake's for a night of karaoke. They pair exchanged a few kisses and shared a moonlit dance on New Year's Eve, but nothing beyond friendship occurred. Their friendship deepened when Alexis turned to Mac after her daughter Kristina had been the victim of physical abuse from her boyfriend Kiefer Bauer. Alexis had accidentally killed Kiefer in a hit-and-run accident. Mac charged her with the crime but immediately released her so she could care for her hospitalized daughter.
Warren Bauer, Kiefer's father, was furious over the death of his son and he accused the police of not doing their job in seeking justice for his son. Warren took matters into his own hands and confronted Kristina in the hospital with a gun. Mac and several other witnesses tried to reason with Warren to no avail. He shot Mac, but Mac was able to fire a return shot which killed Warren. Afterwards, Maxie's new love interest doctor Matt Hunter performed surgery on Mac and saved his life.
A new threat emerged in Robin's life in the form of a doctor named Lisa Niles. She and Patrick shared a night together while Robin was out of town and Robin was hurt by Patrick's betrayal. Mac readily invited Robin and her daughter to move in with him while Robin decided what to do about her marriage. Patrick insisted he wanted to be with Robin, but Lisa made it clear she would not give up her pursuit of him. Lisa deliberately tried to sabotage Robin's reputation and Mac sided with Robin every time Lisa accused her of something, even when Lisa filed official charges against Robin at the police station.
Several officers at the PCPD encouraged Mac to step away from the investigations of any charges between Lisa and Robin due to his conflict of interest. He refused and remained steadfast in his belief that Robin was innocent despite the lack of evidence to confirm Lisa's guilt. He believed Robin's accusation that Lisa had been behind her kidnapping and the fire that destroyed his house. Again, no evidence was found. Eventually, Robin, Patrick, and Mac were able to turn the tables on Lisa and she incriminated herself as she tried to kill Robin under the guise of a gas leak. Mac arrived and arrested Lisa. Afterward she was committed to Shadybrook.
Unbeknownst to Robin or Mac, Lisa escaped from Shadybrook and took a few hostages at the hospital. The hostages were held at gunpoint and they included Robin and Maxie. Lisa locked her hostages inside a conference room and Mac desperately tried to free his girls, even though members of the police force urged him to step back because he was reacting as a parent instead of as the police commissioner. Maxie and Robin both made it out of Lisa's clutches safely and they all believed their problems with Lisa were over after she accidentally injected herself with drain cleaner she had intended for Robin.
Lisa lapsed into a coma but she returned once more to seek her revenge on Robin and Patrick. She boarded a private yacht that Patrick, Robin, and a few other guests were on and tried to inject Patrick with Robin's HIV positive blood. Robin fought Lisa off before she passed out on the ship. When Robin came to and the police arrived, Lisa was missing. She turned up dead a few days later and an autopsy confirmed that Lisa had been murdered. Mac was forced to investigate Lisa's death, even though Robin and Maxie were considered suspects.
Mac shared his suspicions with Alexis that either Maxie or Robin may have killed Lisa. Alexis vowed to represent either woman if need be and Mac appreciated her support. A member of the yacht's staff, First Mate Briggs, eventually confessed to the crime in a suicide note and Mac immediately declared that the case was closed.
Mac made time for a little fun and enjoyed a drunken game of strip pool with Alexis and her friend Diane Miller. Mac became intoxicated and Diane took him home. They slept together that evening and attended a charity event together a few weeks later.
Soon after, Mac's life was filled with grief once again when he learned that Robin had been killed after an explosion occurred in her lab. Mac blamed Jason for Robin's death because she had been in the lab working on a treatment for him when the accident happened. Mac turned to Spinelli and asked him to help Maxie deal with Robin's death. Mac also had a confrontation with his brother when Robert returned to town and learned the news. Robert was determined to see Robin's body, although she had been burned beyond recognition. Mac begged his brother to remember Robin the way she was but Robert refused.
Robert left town before Robin's funeral but Anna was there, along with the rest of Robin's family and friends. Maxie initially refused to attend the funeral but she did show up and claimed that she was responsible for causing the accident that had claimed Robin's life because her purse had caused the gas leak which led to the explosion. Everyone reassured Maxie that she was not to blame but she refused to listen and insisted that Mac arrest her. When he refused, she announced that she had killed Lisa Niles.
All of Maxie's family and friends knew her admission of murder was linked to her feelings of grief over Robin but Mac was forced to arrest her after some details she shared about the murder were corroborated by a witness. Maxie also claimed that she was behind the death of the woman that had confessed to Lisa's murder in a suicide note.
Although Maxie refused legal counsel, Mac hired Alexis to represent her. There was not much Alexis could do since Maxie plead guilty and she was sentenced to twenty years in prison. Felicia returned to Port Charles for the sentencing and both she and Mac were devastated by the verdict. Their despair over Maxie was short lived when Spinelli found video footage which showed a man hitting Lisa over the head with a wrench. Maxie admitted that the unknown man in the footage was Matt and she had been covering for him all along. He had been intoxicated and not recalled his actions.
Maxie would be able to go free in exchange for her testimony that she had seen Matt commit the murder. Maxie convinced Matt to elope so she would be unable to testify against him. Mac was not thrilled by the marriage because he doubted that Matt was good enough for Maxie but he was relieved to have her out of prison.
In the midst of Maxie's legal battle, the mayor removed Mac from his position as police commissioner and gave job to Anna Devane. Mac shared words of encouragement with his former sister-in-law and wished her well. Mac made peace with the mayor's decision and took a job as a bartender at the Floating Rib. He also rekindled his romance with Felicia and they started dating. While the relationship between Mac and Felicia became more serious, Maxie chose to be a surrogate for her best friend and became pregnant.
Felicia sent notification to Frisco regarding Maxie's pregnancy and he arrived in Port Charles to check on Maxie and to win Felicia back. Mac feared that Felicia would leave him for Frisco but instead she declared her love for Mac and proposed to him. He accepted the proposal and presented Felicia with an engagement ring. They married a few months later at The Floating Rib in the presence of their family and friends.
The wedding reception came to an abrupt ending when Maxie went into labor and later gave birth to a daughter. After the delivery, Maxie struggled to accept that the child belonged to Dante and Lulu. Mac and Felicia offered their support to Maxie and she shocked them with the truth that the baby she had given birth to was her own biological child with Spinelli. Both Felicia and Mac remained on Maxie's side when she decided to seek custody of the baby but instead of banned from any contact with her daughter. As Mac continued to worry about Maxie, their family received positive news when Robert emerged from a coma and Robin was revealed to be alive.
Mac was thrilled to be reunited with Robin and he believed that Maxie was in a better place after her spiritual journey until he met her boyfriend Levi. Mac disapproved of Levi and he made his feelings known. To Mac's dismay, Maxie chose to marry Levi but the ceremony was interrupted when Levi was revealed to be a con man after Felicia's Aztec jewels. Levi kidnapped Maxie at gunpoint while his accomplice did the same to Lulu Falconeri. Mac tried to stop the men from leaving with Lulu and Maxie but his attempt was unsuccessful and he was shot by Levi. The injury was not fatal but it prevented Mac from joining the search for Maxie and Lulu.