Natasha Alexenko, who became a powerful advocate for ending the national backlog of rape-kit testing after suffering dual traumas — being sexually assaulted and then discovering that her own rape kit with forensic evidence from her attacker had gone untested for 10 years — died on Oct. 31 in West Islip, N.Y. She was 51.

Her husband, Scott Sessa, said that her death, in a hospital, was caused by complications of amyotrophic lateral sclerosis and multiple sclerosis.

Ms. Alexenko was a 20-year-old filmmaking student at the New York Institute of Technology when she was violently attacked by a man shortly after midnight on Aug. 6, 1993, as she was entering her apartment in Manhattan. Armed with a 9-millimeter handgun, he forced her into an empty stairwell, robbed, sodomized and raped her. Then, with a warning — “Don’t come after me or I’ll kill you!” — he fled.

Although she wanted to take a shower, she went to a hospital for a forensic medical examination. DNA evidence from hair, fibers, blood, semen and saliva that the assailant might have left behind were saved in a box of evidence known as a rape kit.

“As I lay trembling on the cold examination table, with my feet up in stirrups while the medical examiner poked, prodded, combed, snipped, and scrutinized my genitalia for clues to my abductor, I assumed my rape kit would be tested immediately,” she wrote in her book, “A Survivor’s Journey: From Victim to Advocate” (2018). “Why else would I endure such a painful, invasive, and embarrassing exam?”

But the kit was not tested until 2003, just as the 10-year statute of limitations for prosecuting her case was nearly up. (New York State abolished the statute for first-degree rape in 2006.) Ms. Alexenko discovered that she was not alone in losing the precious time available to have her attacker identified, arrested and tried. In the late 1990s, the Manhattan district attorney’s office estimated that 17,000 rape kits sat untested in a police warehouse in New York City. Thousands more had been left untested in crime laboratories nationwide, the result of tight budgets, overburdened crime labs and, some advocates said, a gender bias discounting sexual assaults against women.