RIVERSIDE, Calif. -

Three Marines were convicted today of first-degree murder and other charges in the slayings of a young sergeant and his bride during a home invasion robbery at the couple's French Valley residence.

Jurors must now decide whether to recommend a death sentence or life in prison without the possibility of parole for Kevin Darnell Cox, 25, Emrys Justin Justin John, 23, and Tyrone Miller, 25.

A fourth defendant is awaiting trial.

An eight-woman, four-man jury deliberated less than two days before finding Cox guilty of the Oct. 15, 2008, slayings of 24-year-old Janek Pietrzak and his 26-year-old wife, Quiana Faye Jenkins-Pietrzak.

A separate eight-man, four-woman jury deliberated one day before convicting John and Miller of the crimes.

Both panels also found true special circumstance allegations of multiple murders and that the killings occurred in the course of a robbery and a burglary. Miller was additionally convicted of forced sexual penetration with a foreign object, and John's jury found true a sentence-enhancing allegation of discharging a firearm to produce great bodily injury.

Cox's penalty trial will get underway Monday morning, while Miller's and John's penalty phase will begin in the afternoon.

Cox, clad in a brown suit and standing next to his attorneys, showed little reaction as the verdicts were read, though appeared to be listening intently. After jurors left the room, his gaze fell to the floor and he prodded his chin with his forefingers.

John, dressed in a beige suit, and Miller, wearing a blue T-shirt and casual pants, remained seated as the verdicts were read by Riverside County Superior Court Judge Christian Thierbach. Both men stared straight ahead.

The fourth defendant, 25-year-old Kesaun Kedron Sykes, is slated to be tried in August.

Deputy District Attorney Daniel DeLimon called the defendants "Marines by day and criminals by night." According to DeLimon, the four Marines wanted to get inside the Pietrzaks' two-story house at 31319 Bermuda Ave. because of greed -- and much more.

"This was about having the power to see the fear in somebody's eyes. It's about taking pleasure in the sexual humiliation of a woman and tormenting her husband by making him watch," the prosecutor said.

DeLimon quoted one of the defendants describing the 90-minute ransacking of the victims' property and abuse of the couple as "party time."

DeLimon said Cox attempted to minimize his participation in the slayings. But the statements he made to friends afterward and the testimony of Miller revealed that Cox was an active perpetrator, according to the prosecutor.

He said all of the men pummeled Pietrzak, while Cox was delegated with the responsibility of binding the couple to immobilize and silence them. Cox also planted false evidence in an attempt to throw off authorities, directing his associates where to paint epithets such as the "n" word to make it appear as though the crime was racially motivated, according to DeLimon.

Quiana was black, and her husband of 68 days, a native of Poland, was white.

Miller testified that he was displeased with Pietrzak because the sergeant had told the lance corporal that his chances of being promoted to corporal were nil.

Cox told investigators that he rang the doorbell twice shortly after 1 a.m., and Pietrzak came downstairs in a T-shirt and boxer shorts, deactivated his house alarm and opened the front door. The defendants, armed with shotguns, beat the young sergeant into submission, DeLimon alleged.

According to the prosecutor, Miller and Sykes stripped Quiana and used a vibrator they found in the couple's bathroom to violate her sexually. John shot the victims execution-style with a 9mm handgun.

All of the men served in a helicopter maintenance squadron at Camp Pendleton.