LANSING, Mich. — Armed with pieces of paper etched with their memories of sexual abuse, they stepped forward, one by one — nearly 100 of them, with more to come.

For four full days this week, in a fluorescent-lighted courtroom here, women and girls — some of them the best gymnasts in the country, others with dreams prematurely crushed, they said, by a man who now sat in handcuffs 10 feet away — leaned into a microphone to address him, sometimes through sobs, sometimes with screams, but always with determination.

Aly Raisman, 23, who won gold medals at the past two Summer Olympics, told of late-night knocks on her hotel door while she was competing overseas, as the man, Dr. Lawrence G. Nassar, then the team doctor, arrived to abuse her.

A teammate at the 2012 London Games, Jordyn Wieber, who until Friday had not identified herself as a victim of Dr. Nassar’s, recalled the torment of the Games, where she was a part of the American team that won a gold medal but, she said, had to submit to his care under the auspices of the sport’s governing body, U.S.A. Gymnastics.