Transgender Murder Trial Set to Begin Today

April 14, 2009— -- A pretty Colorado teenager was found beaten to death with a fire extinguisher last year after her date allegedly found out that she was transgendered and had male genitalia.

That murder has become a ground breaking legal case since it will be the first time an anti-transgender murder will be prosecuted as a hate crime under state law, according to the Gay and Lesbian Alliance Against Defamation.

A coalition of anti-violence groups have put out an ad using the case to lobby for national hate crimes legislation.

The trial opens today in Greeley, Colo.

Police say Allen Ray Andrade, 32, snapped when he learned that 18-year-old Angie Zapata, who was born Justin Zapata but lived as a young woman, was biologically a man.

Andrade admitted to investigators that he beat Zapata first with his fists and then with a fire extinguisher, according to a Weld County arrest affidavit obtained by ABCNews.com.

He allegedly told investigators he thought he "killed it," referring to Zapata, before hitting her again with the fire extinguisher as she tried to get up, the affidavit says.

Zapata's body was discovered by her sister on July 17, 2008, inside her Greeley, Colo., apartment. She had been fatally beaten, with blunt force trauma around her head, according to the Weld County Coroner's Office.

Andrade told investigators that he and Zapata met on the social networking Web site MocoSpace, according to the affidavit. They arranged to meet and on July 15.Andrade, who has a criminal record in neighboring Adams County, said that Zapata attended a court hearing with him. Later that day, Zapata allegedly performed oral sex on Andrade but refused to let him touch her sexually.

The following day, according to the affidavit, Zapata left Andrade alone at her apartment. The suspect told investigators that he noticed photographs that, coupled with her reluctance the previous day, raised questions about Zapata's sex.

Later on July 16, Andrade said he asked Zapata outright whether she was a man or woman. "I am all woman," Zapata allegedly told him, according to the affidavit. He asked for proof and when she refused, Andrade told investigators, he "grabbed Zapata's genital area and felt a penis."