INDIANAPOLIS -- Mike Tyson's 18-year-old accuser delivered a stunning account of her alleged rape in three hours of testimony and cross examination yesterday afternoon.

In painful and exacting detail, delivered with the voice of a child, the tiny 108-pound Miss Black America contestant persuasively gave her version of what happened here on the morning of July 19. The young woman's testimony is the core of the prosecution's case against Tyson.

Portrayed in opening statements by prosecutors as a naive, star-struck young girl, she was villified by Tyson's defense lawyers as a manipulative, money-hungry woman who wanted a long-term relationship with the prize fighter.

But on her first day of testimony, wearing a gray suit and white blouse, this is what the jury saw:

An honor student from a middle-class black family who looked much younger than a college freshman; a Sunday school teacher and former cheerleader, a class office-holder with a resume full of public service, from serving in the Big Sisters program to winning competitions to travel to Washington and the Soviet Union in student exchange programs.

As she spoke, the jury shifted its gaze from the witness stand to the burly, former world heavyweight champion. She did not cry.

As she told her story, he jammed a blue pen into his mouth, twirling it there and chewing on it until she stopped.

"I was terrified. I said, 'It's time for me to leave,' " the young woman told the court as she recalled begging Tyson to leave her alone.

"I pulled back and he said don't fight him. I tried to fight him. I was punching him. It was like hitting a wall."

In describing her account of the alleged rape, the young woman recalled being humiliated and forced to endure "excruciating pain."

"My eyes were just filling up with tears. I kept saying, 'Please let me go.' And he just laughed -- like it was a game."

Tyson has maintained his innocence, saying that the woman freely consented to have sex with him. His lawyer, Vincent Fuller, said yesterday that Tyson would testify in his own defense.

Tyson, who became the youngest man ever to win the world heavyweight championship in 1986, at age 22, is alleged to have raped the woman in his room of the Canterbury Hotel on July 19.

He is the only athlete of his stature to be charged with such a violent crime. Because of his ferocious fighting style, Tyson has become a living symbol of physical power.

His life is perhaps a modern tragedy as well -- a superbly talented man with a self-destructive personality.

If the jury believes the woman's story and if his lawyers are unable to damage her credibility with the jury during cross-examination today, Tyson may be returned to where he was before he learned to box when he was 13:

In a guarded state institution, living a regimented lifestyle and fighting for emotional and physical survival.

When Fuller, his defense lawyer, made opening statements to the jury, he portrayed Tyson as an unfortunate brute, without a family, a high school diploma, or ability to speak well in public.

"Who is Mike Tyson?" Fuller asked. "He's a remarkable boxer . . . trained to do only one thing -- to defend himself in a ring and to go to battle like a warrior."

In a stiff, formal delivery that contrasted markedly with prosecutor Greg Garrison's folksy manner, Fuller said his client's accuser was "sophisticated," that she promised other Miss Black America contestants that she would get money out of Tyson, as did the boxer's ex-wife, television actress Robin Givens.

Fuller said the accuser came to Tyson's room at the Canterbury Hotel knowing they would have sex. And when Tyson refused to accompany her downstairs after the act, she was infuriated.

"He was rude," Fuller said, "but she was disillusioned and angry."

Both sides in the case agree Tyson met the girl during a rehearsal for the beauty pageant and had agreed to go out on a date. She gave him her telephone number at the Omni Hotel. He called her at about 1:30 a.m. on July 19.

At the rehearsal, he was wearing a large button that said "Together in Christ," and when they met, Tyson flirted with her, saying, "You're a nice Christian girl, right?" the young woman recalled.

Later, when he called her room, she said she told him it was too late to go out. She suggested he come up to visit with her and two other roommates. This was corroborated by another roommate's account.

But the young woman said she relented, agreeing to go out with Tyson to some parties going on after a concert that evening. She said she took her camera.

When they got into the limousine, she said Tyson told her they had to stop at his room to make a quick phone call. She told the jury she waited in another room of his suite as he picked up the bedroom phone and turned on the television there.

"Then he said, 'Come here, I want to talk to you,' " she said.

The young woman said she entered the bedroom and sat at the foot of the bed. She said they talked about her family. She said he mentioned he raised pigeons.

"I said, 'Let's go,' but he said, 'I already have an idea. You're probably daddy's little girl aren't you?' I said something smart, like 'You haven't met them yet,' and he leaned over, his voice changed and everything and he said 'You're turning me on.' "

She said she rose from the bed and went to the bathroom, telling Tyson she expected they would leave when she returned.

When she again opened the door, she testified, Tyson was on the bed dressed only in his undershorts.

She said he grabbed her, forced her onto the bed and removed her clothes as she fought him without success, testifying to the intense pain he caused.

After begging him to stop, she said she continued to fight the 235-pound boxer, yelling that she did not want to become pregnant or be infected with a disease.

"I don't have anything and I know you don't," she recalled Tyson as saying as she said he began raping her.

"I was trying to fight him. I was trying to do a lot of things. He kept saying, 'Don't fight me. Relax. Don't fight me Mommy . . . ' And his eyes got evil."

She said she got up, dressed and left the hotel. She said she was driven to her hotel by Tyson's limousine driver. She later told friends that Tyson "tried" to rape her, because, she said, she was embarrassed.

Ultimately, she told roommates and her parents that she was raped and reported it to authorities.