CAMBRIDGE, Mass--Before Vuthy Seng was sent away forever yesterday, a prosecutor asked that his three life sentences be served one after the other.

Assistant Middlesex District Attorney Rick Grundy said his request, which was granted, was a symbolic way of emphasizing the lost lives of the three children Seng was convicted of murdering.

"These were separate and distinct individuals," Grundy said. "They came into the world separately and they left the world separately."

Family members said Seng was angry after Chhong Yim told him to move out of her apartment because her children did not like him.

Seng was charged with shooting to death 9-year-old Sovanna Men, 15-year-old Visal Men, and 12-year-old Virak Men. The three died of their wounds in the week after the November 1995 attack.

The fourth child, Sathy Men, escaped and recovered from a gunshot to her head. Now, 16, she testified as one of the key prosecution witnesses.

Yim thanked friends and supporters after the verdict.

"Not a day went by when me and my daughter didn't think of my three sons," she said, speaking through an interpreter outside the courtroom.

During the trial, defense lawyers conceded that Seng shot the children, but said he was insane at the time of the killings.

On Monday, lawyer Dan Callahan described Seng as a "destitute and broken" man who was hearing voices--and should not be held criminally responsible.

Callahan said Seng's mental troubles stemmed form a 1993 accident at a bottling factory in which he struck his head when a stack of crates fell over on him.

Grundy said yesterday that Seng will undergo a psychiatric evaluation at Bridgewater State Hospital, where he has been held for much of the time since the slaying.

"His lawyers have refused to allow him to be evaluated for the entire time he's been there," Grundy said. "I suspect that evaluation will take place and they'll learn quite quickly that he is not suffering from any kind of psychotic condition and he will be sent to prison."