HARRISBURG — A Penn State assistant football coach testified today that he believes he saw former assistant coach Jerry Sandusky sexually molesting a boy but said he wasn’t 100 percent sure it was intercourse.

Mike McQueary, speaking for the first time in public about the 2002 encounter, said he truly believes what he saw in a Penn State locker room was intercourse.

McQueary took the stand today in a courtroom against two school officials accused of lying to a grand jury about the child sex-abuse allegations against Sandusky.

McQueary said he saw Sandusky was behind a boy he estimated to be 10 or 12 years old, with his hands wrapped around the boy’s waist. He said the boy was facing a wall, with his hands on it.

He said he peeked into the shower several times and that the last time he looked in, Sandusky and the boy had separated. He said he didn’t say anything, but “I know they saw me. They looked directly in my eye, both of them.”

His testimony came during a preliminary hearing for two school officials accused of lying to a grand jury about child sex-abuse allegations against former coach Jerry Sandusky.

McQueary told a grand jury that he told the administrators, Tim Curley and Gary Schultz, that he saw Sandusky sodomize a boy in a locker room shower in 2002.

Curley and Schultz are charged with lying to a grand jury and failing to properly report what McQueary allegedly told them. Their lawyers say the men are innocent and contest McQueary’s statements

District Judge William C. Wenner was hearing testimony today to help him decide whether state prosecutors have enough evidence against the pair to send their cases to trial.

Sandusky says he is innocent of more than 50 charges stemming from what authorities say were sexual assaults over 15 years on 10 boys in his home, on Penn State property and elsewhere. The scandal has provoked criticism that Penn State officials didn’t do enough to stop Sandusky.