SOUTHFIELD, Mich. (AP) _ A drifter accused of killing a college student he met through her research project on prostitution told police he wanted ``to put her out of her misery'' from mounting money troubles.

At his arraignment Thursday, Kenneth Tranchida declared, ``I'm guilty.'' But no plea was entered, and Judge Stephen Cooper urged him to speak to a lawyer.

Tranchida, 41, was jailed without bail after he was arrested Tuesday and charged with first-degree murder. He could get life in prison without parole if convicted.

Tina Biggar, a 23-year-old undergraduate psychology student at Oakland University in Michigan, was working on a research project on prostitutes and AIDS when she disappeared Aug. 23. The project was funded by the government's Centers for Disease Control and Prevention.

Her body was found Sept. 21 in the Detroit suburb of Southfield, behind a house where one of Tranchida's relatives once lived, police said.

Biggar's car was found in Tranchida's possession, police said, and tests found her blood in the trunk. An autopsy showed she died of blows to the head and neck.

Authorities believe she was killed the day she disappeared.

``The one reason he gave was that she was complaining about her financial woes,'' Assistant Prosecutor Gary Tunis said. ``She needed money, so he wanted to put her out of her misery.''

Police said Biggar had interviewed prostitutes in prison and on the streets for the project and had gone to work for an escort service, where she met Tranchida, who was a customer.

William Dwyer, the police chief in Farmington Hills, where Biggar lived, wouldn't say what Biggar did at the service or elaborate on the nature of her relationship with Tranchida. He has served time for breaking and entering and was a habitual criminal.

Biggar had transferred to Oakland University from South Dakota State University to be closer to her parents. Her father is commander of the Coast Guard's Traverse City station.