By Ian Simpson

BELLEFONTE, Pennsylvania (Reuters) - Prosecutors in the fast-paced Jerry Sandusky child sex abuse trial are close to wrapping up their case, with three alleged victims still to testify against the former Penn State assistant football coach.

Testifying on Wednesday, three witnesses accused Sandusky, 68, of sexually abusing them in showers, bedrooms and basements when they were young boys. At least once the former coach threatened an accuser to keep him quiet, according to testimony.

Judge John Cleland told jurors at the close of Wednesday's session in Centre County Court that the trial was running much faster than expected. The prosecution, which began presenting evidence on Monday, could conclude its case by Friday.

"It would appear that by Friday the commonwealth will have enough time comfortably" to finish, he said. At the trial's start, Cleland had said it would go on until the end of the month.

Sandusky, once defensive coordinator for Pennsylvania State University's high-powered football program, faces 52 counts of abusing 10 boys over a 15-year period in various places including the school's locker rooms. If convicted on all counts, he faces a sentence of more than 500 years in prison.

The scandal scorched Penn State and its football program when grand jury charges were announced in November 2011. It also has focused the spotlight on the issue of child sexual abuse.

Of the alleged victims - known in court documents as Victims 1 to 10 - eight agreed to testify against Sandusky. Five have completed their sometimes-graphic testimony, including accounts of oral sex. Two of the accusers remain unidentified.

The defense, led by attorney Joe Amendola, has said it could call dozens of witnesses when it presents its case. They include Sandusky's wife Dottie and other family members.

Amendola has argued that the accusers are out for money. He has said that Sandusky might have acted inappropriately but is not a molester.

The trial is taking place amid a heavy media presence in the small town of Bellefonte, about 10 miles northeast of State College, site of Penn State's main campus.

Sandusky, who retired in 1999, is accused of meeting the boys through a charity he began, the Second Mile.

The charges against Sandusky prompted the firing of university President Graham Spanier and head football coach Joe Paterno, record-holder for most wins by major U.S. college football coaches. Paterno died of lung cancer in January.

Reuters' policy is not to identify victims of sexual crimes.

(Editing by Mohammad Zargham)