Chander Matta, charged in the slayings of three Washington area prostitutes, will plead insanity as a defense, according to his attorneys.

Arlington County Circuit Court Judge Paul F. Sheridan granted a request on Tuesday by Matta's attorneys, Paul H. Zuckerberg and Arthur M. Reynolds Jr., to postpone the trial to give them time to complete Matta's psychological evaluation.

Matta, 21, was charged in June with robbing and slaying Jodie Marie Phillips, Sherry Larman and Sandra Rene Johnson during the Memorial Day weekend. Each of the women was killed by asphyxiation within 36 hours.

Prosecutors have argued in court that Matta systematically killed each of the women after having sex with them, using a choke hold he learned at a military academy and wrapping a plastic bag over their heads. Each of the victims, the prosecution claims, was robbed of money or other items of value.

After the slayings, according to the prosecutors, Matta returned to perform his job as an airport attendant, before killing his next victim.

Deputy Commonwealth's Attorney Arthur Karp said he was "not surprised" by the insanity defense, "because we've got a confession and we've got evidence" linking Matta to the slayings.

Although Reynolds has indicated that he might file a motion requesting a supression of the confession, no such motion has been filed, Karp said.

If convicted of those slayings, Matta faces a maximum penalty of life imprisonment.

Under Virginia law, there are two types of insanity defenses, Karp said. In one, a defendant claims not to know right from wrong.

In the second, which Matta's attorneys are expected to use, the defendant claims to be "suffering from a mental disorder and that, even though he knows right from wrong, he has an irresistible impulse" to commit the crime.

Over the next several weeks, Matta will undergo a battery of psychological and neurological tests, which will provide evidence to be used by both defense and prosecution, Karp said.

Karp said the first examination, for the defense, will be conducted this morning at the Neurological Center in Falls Church.

Karp said that psychologists at the Institute of Law, Psychology and Public Policy in Charlottesville have been retained to conduct a psychological test of Matta this month for the prosecution.

Matta was to have stood trial on Oct. 22 on charges stemming from Phillips's slaying.

That trial has been postponed until Nov. 26.

The Larman and Johnson murder trials have been rescheduled for Dec. 10 and Jan. 14 respectively.