BELLEFONTE, Pa. — A Penn State University policeman told Jerry Sandusky, the former assistant football coach who has been charged with sexually abusing 10 boys over 15 years, that he should not shower with young boys, according to testimony provided Thursday on the fourth day of Sandusky’s trial.

The testimony was provided by Ronald Schreffler, who, as a Penn State police investigator, spoke with Sandusky in 1998. Schreffler had received a report from the mother of an 11-year-old boy who said he had showered with Sandusky at a locker room on the Penn State campus.

The boy, now 25, also testified Thursday, saying he met Sandusky at the former coach’s Second Mile youth charity for children from troubled homes. The accuser said he felt uncomfortable being naked with Sandusky, who, he said, urged the boy to take a shower after a workout even though they had not sweated that much.

“I remember seeing his chest hair and thinking, `This is icky,”’ he said, adding that Sandusky tickled him and described himself as the tickle monster.

The accuser said he blacked out and did not remember what happened after Sandusky lifted him up to the shower head to wash the shampoo out of his hair. When he returned home later that day, he told his mother he had showered with Sandusky.

The man was the sixth alleged victim to testify against Sandusky. His mother’s decision to alert the police prompted the earliest known investigation into Sandusky’s behavior cited during the trial.

Cross-examined by Sandusky’s lawyer, Joseph Amendola, the accuser said that he had no recollection of sexual contact with Sandusky and that he continued to communicate with him for many years.

A seventh alleged victim testified that he had sexual contact with Sandusky when he was a boy. He stayed at Sandusky’s house about 50 times over three years. He, too, was persuaded to shower with Sandusky, who also gave him gifts like football tickets. The boy was later sent to a group home for delinquent children and was under foster care.

The trial was initially expected to last three weeks, but it now appears it may continue for only two.