Indirectly responsible for the death of Mr. Rice-- while Doug Cassen and Bob Hughes were saving Claire from her suicidal overdose (Mr. Rice, a patient of Doug's, died from a duodenal ulcer that Doug was not there to treat 
Under pressure from Judge Lowell, committed perjury during Edna Rice's malpractice suit against Doug; lied that the Judge had a heart attack when she was being saved from her drug overdose (she later recanted and saved both Doug's career and her marriage) 
Stabbed Michael Shea in a drunken rage 
Wealthy Claire Lowell was the best friend of Nancy Hughes. Neglected by her husband, Jim, Claire continually was in a state of depression which worried her daughter, Ellen. Despite being in a loveless marriage with a husband who was no longer living at home, Claire was adamant about remaining with Jim in order to retain a sense of propriety. The end of the Lowell marriage occurred when the secret affair between Jim and Nancy's sister-in-law, Edie Hughes, became known. Though Claire succeeded in getting Jim to return home for Ellen's sake, Jim decided they'd be in separate bedroom. Sinking further into her depression, Claire accidentally overdosed on sleeping pills, although Jim accused her of doing it deliberately. Soon, Claire became clinically depressed and actually began to appear suicidal. One person especially concerned for Claire was her doctor, Doug Cassen. Offended by Jim's cavalier attitude toward his wife, Doug became a great friend to Claire and persuaded her to see a psychiatrist. Through therapy, Claire was able to see that she never really loved Jim and married him only because her family had expected it. Finally realizing the folly of her marriage, Claire told Jim she'd grant him his divorce. Tragically, before the divorce was finalized, Jim lost his life in a boating accident.
Soon after Jim's death, Claire discovered how much Doug cared for her and the two married. Though her beloved father-in-law, Judge James Lowell, objected to her marrying so soon after Jim's death, he soon realized that Doug was a much better husband than Jim ever was. However, it didn't take long for Claire to discover that medicine was Doug's first priority. Lonely at times, and sometimes jealous over his friendships with women, Claire decided to enjoy a social life away from her husband and ended up becoming attracted to Bill Abbot, a business associate of her brother. That attraction would lead the pair to end up kissing in a parked car that was hit! Although the couple was fine, the truth about what they were doing came out and Doug demanded that she never see Bill again. Though she refused to comply, Bill didn't want to destroy the Cassen marriage and left Oakdale. However, Claire continued to be withdrawn and depressed until Doug feared that he might have to divorce her. Shocked, Claire became convinced that Doug was seeing another woman and again overdosed on sleeping pills. Though Doug and young doctor Bob Hughes found her and were able to save her life, it almost happened at the cost of Doug's career when a patient of Doug's died. Being sued because he didn't respond to the message, he and Judge Lowell were anxious to preserve Claire's reputation and concocted a lie that Doug had been treating the Judge for a heart condition. Though severely withdrawn, at the last moment, Claire found the courage to walk into the courtroom and testified that Doug was saving her life.
Afterward, the couple's marriage remained on track. One sense of concern, however, was Doug's favoritism toward young doctor, Neil Wade. When Doug strangely offered a staff position at Memorial to Neil, rather than Doug's former protégé, Bob Hughes, a shocked Claire and Judge Lowell confronted Doug. Doug was forced to admit the truth--Neil was his long lost son! Again feeling neglected because of Doug's preoccupation with Neil, Claire was horrified when Judge Lowell almost died because a panicked Neil ran instead of treating him. Horrified that she almost lost her beloved father-in-law because of Neil's incompetence, Claire demanded that Doug stay out of his life, although she later relented. Later, Doug would suffer a fatal concussion from a head wound after the angry husband of a former patient violently shoved him.
Following Doug's death, Claire surprisingly found herself being wooed by the charming, young Dr. Michael Shea. Despite concerns from family and friends, Claire and Michael quickly eloped. However, it didn't take long to discover that this marriage was a serious mistake. Soon after the marriage, Claire developed a drinking problem which was aggravated by Michael's extreme neglect and sudden disinterest in her. Finally, Claire learned the reason for Michael's disinterest--he was having an affair with Bob Hughes's ex-wife, Lisa, who had given birth to his son! Though she initially refused Lisa's pleas to divorce Michael, when she was confronted with a signed affidavit stating that Michael was the father of Lisa's baby, the news was too much for her and Claire divorced Michael, who lost his job at Memorial over neglect of a patient. Though Michael was almost able to charm her into taking him back, when she overheard him say he was only using her for her money and connections, an enraged Claire went on a drunken binge and ended up stabbing him with a letter opening! However, instead of turning in Claire, Michael lied and covered up the crime, in return for being reinstated at Memorial.
Finally free of Michael, Claire decided to settle for a quiet life as a single woman and concentrated on Ellen. Especially troubling was the attitude of Ellen's oldest son, Dan, who was conceived when Ellen was a teenager and given up for adoption. When Dan learned that his new stepmother was actually his biological mother, he turned away from her. Claire had become quite angry at Dan for the way he treated both Ellen and David when Dan found out about his true parentage. Dan got mad at Claire, as well, when he learned that she knew the truth too, and nearly severed all ties with Claire. However, Dan wanted to bury the hatchet after he met Liz Talbot and went to the Lowell house and begged Claire's forgiveness for his treatment of her. At first, Claire refused, but as Dan was walking out the door to his car, she realized how important he was to her and ran out the door to apologize and make amends. Unfortunately, Dan was in his car, quite a distance from the house, and Claire ran out in the street not watching where she was going. Tragically, Claire was hit by a passing motorist and would die at Memorial shortly thereafter, although not before getting the chance to make amends with Dan.