VISTA, Calif. (AP) _ A widow and five Marines have been ordered to stand trial on charges of murder and conspiracy for allegedly plotting the death of the woman's husband, who was shot and then run over by a car.

Vista Municipal Court Judge Luther Leeger, in a ruling Friday, said there was sufficient evidence to hold the six for trial in the slaying of Marine Staff Sgt. Carlo Troiani, 37.

Leeger's ruling followed a three-month preliminary hearing for the defendants, all of whom were ordered held without bail pending an April 5 arraignment in Superior Court.

Troiani, 37, was shot several times and then run over by a car on the night of Aug. 10 on a rural road in Oceanside, after being lured there on a ruse that his wife's car had broken down, Deputy District Attorney Larry Burns said.

Burns said Laura Troiani, 23, allegedly was having an affair with one of the Marine defendants and promised each of the five men a share of Troiani's $35,000 military life insurance if they killed him.

The ambush was preceded by unsuccessful attempts on Troiani's life, including a failed effort to blow up his car by wiring the ignition system to its gasoline tank, Burns said.

Leeger upheld special allegations for four of the defendants which could lead to the death penalty if they are convicted.

Ordered to stand trial for capital murder and conspiracy, in addition to Mrs. Troiani, were Lance Cpl. Mark J. Schulz, 19, of Stevens Point, Mich. the alleged gunman; Lance Cpl. Jeffrey Mizner, 21, of Holt, Mich., Laura Troiani's reputed lover; and Lance Cpl. Russell A. Harrison, 19, of Brooklyn N.Y., who was allegedly at the shooting scene with Laura Troiani and Schulz.

Ordered bound over to Superior Court for trial for non-capital murder and conspiracy to commit murder were Lance Cpl. Russell F. Sanders, 20, of Michigan Center, Mich., who allegedly helped lure the sergeant to his death, and PFC Kevin W. Watkins of Carmichael, Calif., 20, who allegedly brought some of the others back to Camp Pendelton on his motorcycle following the shooting.