An 18-year-old man who allegedly asked police after his arrest if he could be held responsible for doing something while on medication was ordered to stand trial on a charge of fatally stabbing his ex-girlfriend.

John Mullarkey Jr., of Monroeville, stabbed Demi Cuccia, 16, on Aug. 15 and then slashed his own throat, police said. His attorney said the teen was taking Accutane, an acne drug that the U.S. Food and Drug Administration has linked to episodes of suicide and depression.

Allegheny County Detective Mike Kuma testified Friday that he communicated with Mullarkey using a message board while Mullarkey was recovering from his neck wound. Kuma said Mullarkey asked him, without prompting, about a medicated person being held responsible for his actions.

After the hearing, defense attorney Robert Stewart said he's not sure if he will use his client's use of Accutane as a defense at trial because, at this point, he's not willing to concede that Mullarkey stabbed Cuccia.

"But he was taking Accutane and if you just look on the Internet at the drug Accutane it has a significant history of causing side effects, including suicidal ideations and aggressive behavior," Stewart said.

Cuccia attended Gateway High School in Monroeville, a suburb about 15 miles east of Pittsburgh, where she was a cheerleader. Mullarkey had graduated from the school.

Students and others who knew the couple said their relationship had been troubled.

Witnesses quoted in a police complaint said Cuccia spoke about receiving a text message from Mullarkey the day before she was killed — her 16th birthday — in which he threatened to harm her. Another witness told police the couple had a "loud, violent" argument at her home on Aug. 12.

At Friday's hearing, witness Gail Slomer testified she was visiting her daughter on Aug. 15 when she heard "bloodcurdling screams" come from the town house next door.

Cuccia came out of the house and yelled, "I hate you. He stabbed me. He stabbed me. I hate you," as Mullarkey followed her out, Slomer testified, according to a story on the Pittsburgh Post-Gazette Web site. Slomer said Cuccia then grabbed her and both fell to the ground as Cuccia lost consciousness.

A police affidavit, citing an autopsy report, said Cuccia was stabbed 16 times and died from a stab wound to her shoulder that caused her to bleed to death.

Mullarkey claimed Cuccia was stabbed only two or three times with a 3.5-inch blade, Kuma testified Friday.

Police have said Mullarkey nodded when police asked him whether the knife was in Cuccia's home. Police found the weapon, a folding knife with a 3.5-inch blade, on the living room floor.

Mullarkey has pleaded not guilty to the charge. After Friday's hearing, he was returned to the Allegheny County Jail, where he was being held without bond in a special medical unit.

Mullarkey is still recovering from the deep slash wound to his throat. He speaks with a rasp but no long-term effects are expected, Stewart said.