SLIPPERY ROCK — A man is headed for trial on charges he sexually assaulted three girls and provided marijuana to a fourth at underage drinking parties in northern Butler County this year and in 2013.

Alexander K. Klein, 20, of Brady Township on Wednesday waived his preliminary hearing in each of four cases before District Judge Tim Shaffer.

State police filed the cases in September after investigating reports that Klein had sex with several girls at weekend parties in May at his friend’s trailer home in Brady Township.

Klein’s attorney, Joseph Nash of Slippery Rock, declined to comment about the charges after he told Shaffer his client was giving up his right to a hearing in all the cases.

Investigators interviewed two girls who claimed Klein assaulted them at different parties.

One of the girls, a 14-year-old, recounted that she and Klein went into a bedroom where Klein tried to have sex with her. She told him to stop but then passed out, according to court documents. When she awoke, Klein was lying naked beside her.

Police interviewed Klein at the barracks on May 30, a day after speaking to the girl. He admitted having sex with her, documents said.

Klein claimed he and the girl had previously dated and that he believed she was 17 until he recently learned she was 14.

He is charged in that case with statutory sexual assault, corruption of minors, all felonies, and indecent assault, a misdemeanor.

A 13-year-old girl told police that Klein sexually assaulted her at the same Brady Township trailer but at a different drinking party in May.

The girl recounted that during the party she and Klein were in a spare room. There she claimed he held her down and performed intercourse, court documents said.

During an interview with police, Klein acknowledged being at the party and drinking. He told investigators that he and the girl had consensual sex. He claimed she told him she was 17.

He is charged in that case with statutory sexual assault, corruption of minors and indecent assault.

During their investigation, police spoke to another alleged victim who claimed that Klein had sexually assaulted her in 2013 at a home in Slippery Rock Township.

The accuser, who is now 18, said she was 16 in July 2013 when she had gone to the home to attend a friend’s 16th birthday party.

She recalled that almost everyone there was smoking marijuana and drinking. She admitted that she passed out. The next morning she awakened and Klein was lying next to her, naked.

She told investigators that when she got up she felt like she had sex, a police affidavit said, but did not remember.

The accuser also claimed that she did not speak to Klein after that night until this past May, when he allegedly acknowledged that the two had sex.

But when police interviewed Klein about her claims, he denied her claims.

He is charged in that case with statutory sexual assault, aggravated indecent assault and corruption of a minor.

Meanwhile a 16-year-old girl told police that Klein provided her with marijuana at yet another party in May at the same Brady Township home.

She acknowledged the two had consensual sex that same night. But Klein, during his police interview, denied they had sex.

He is only charged in that case with a misdemeanor count of corruption of minors.

Klein remains in the Butler County Prison on $165,000 bail.