Prosecutors said Wednesday they are seeking a DNA sample from a former Boston University medical student charged with killing a masseuse he met on Craigslist, but the man's lawyer would not say whether he will turn it over voluntarily.

Philip Markoff, 23, has pleaded not guilty in the April 14 fatal shooting of Julissa Brisman, of New York City, and the armed robbery four days earlier of a Las Vegas woman, both at Boston hotels.

Rhode Island prosecutors also announced Wednesday his indictment in an alleged attack on a stripper during the same week.

Click for the indictment.

SLIDESHOW: 'Craigslist Killer' Case

Authorities say he met all three women through Craigslist, a classified advertising Web site.

During a pretrial hearing in Suffolk Superior Court, Assistant District Attorney Ed Zabin said he has no known sample of Markoff's DNA and wants Markoff to turn one over.

Markoff's lawyer, John Salsberg, declined comment after the hearing when asked if Markoff will give a sample without being ordered to do so by a judge.

A county grand jury in Rhode Island, indicted Markoff Tuesday on charges of assault with a dangerous weapon and assault with intent to commit robbery in an alleged attack on a Las Vegas stripper at the Holiday Inn Express in Warwick, R.I.

The stripper, who offered lap dances, has told Rhode Island authorities that she was bound with a cord and held at gunpoint on April 16 by a man she met through Craigslist. She said her assailant fled when her husband came to the hotel room. An arrest warrant was later issued for Markoff.

Investigators linked Markoff to the hotel through his fingerprints on a wall and believe he sent text messages from there.

Markoff has been ordered held without bail and is currently in a Boston jail awaiting trial.

Markoff must resolve the Massachusetts cases before he can be brought to Rhode Island to stand trial, said Michael Healey, a spokesman for the state attorney general's office. Each Rhode Island charge carries a maximum of 20 years in prison.

Read the charges against Markoff.

Rhode Island Public Defender John Hardiman said Wednesday he expected his office would represent Markoff, but he said he had not yet reviewed any evidence and could not discuss the case.