BELLEFONTE, Pennsylvania (Reuters) - The judge in the trial of former Penn State football coach Jerry Sandusky on Thursday issued final instructions to jurors ahead of deliberations, telling them a sex abuse conviction must be based on more than whether a child "feels uncomfortable."

Judge John Cleland also threw out three charges against Sandusky. The one-time coach still faces 48 criminal charges related to child sex abuse allegations.

As lawyers prepared for closing arguments, Cleland instructed the jury of seven women and five men in Centre County Court that the motivation of the defendant is crucial to the case.

"The critical issue is not that the child feels uncomfortable ... the issue is not what the child felt, the issue is what the adult intended," he said.

The defense wrapped up its case on Wednesday after little more than two days of testimony without calling Sandusky, 68, to the stand despite a packed courtroom that had hoped to see him testify.

The white-haired former assistant coach is accused of abusing 10 boys over a 15-year period, sometimes in Pennsylvania State University locker rooms. He faces more than 500 years in prison if convicted on all counts.

A long line of spectators on Thursday waited outside the courthouse to get a seat for final arguments in a case that has put renewed attention on the issue of child sexual abuse in the United States and prompted the firing in November of Penn State President Graham Spanier and head football coach Joe Paterno.

Paterno, who won more games than any major college coach, died of lung cancer in January.

One of the spectators, Kay Reyes, a retired Latin teacher, said she had driven from her home in Tuscaloosa, Alabama, with her daughter, a lawyer, to attend the trial.

"If this didn't involve famous people, this would be a slam dunk for the prosecution," said Reyes, who was carrying a sign that said "The Victims = True American Heroes."

The accusers "are the ones who throughout all this have shown bravery, valor and dignity," Reyes said.

Eight alleged victims, now aged 18 to 28, testified for the prosecution last week. They described in often-graphic detail about meeting Sandusky as boys through his charity, the Second Mile, and then being abused, including by groping, shared showers and oral and anal sex.

In dismissing several charges on Thursday, Cleland said that the testimony of one of the victims, Number 4, failed to support two of the counts, while a third count was duplicative.

As for the defense, witnesses who vouched for Sandusky's character as a leading figure in the community played a major role. Daniel Filler, a law professor at Philadelphia's Drexel University, said the character testimony could be enough for the jury to deadlock on the charges.

"The best thing they (the defense) have going for them is the goodwill in the community," he said. "Their main goal is to hang the jury and argue for an acquittal."

Sandusky's wife of 45 years, Dottie, testified for the defense on Tuesday that she had never seen him behave inappropriately with young boys.

The defense also scored points by playing a tape recording of investigators' interview with an alleged victim in which they told the man about allegations from other accusers.

(Editing by Paul Thomasch and Jim Loney)