MURRIETA, Calif -- A judge is scheduled to decide Friday to determine if four Camp Pendleton Marines will stand trial for the robbery-murders of a USMC sergeant and his wife, who was also sexually assaulted, in their Winchester home in Riverside County.

The preliminary hearing at the Southwest Justice Center is expected to last two non-consecutive days.

Kevin Cox, Emrys John, Tyrone Miller and Kesuan Sykes, reportedly nicknamed "Psycho" by the others, are charged with two counts each of first-degree murder and special circumstance allegations of murder during a robbery, committing multiple murders and murder during a rape. John, 19, is additionally charged with personal use of a firearm.

The district attorney's office plans to seek the death penalty for the men -- all but John are 21 years old -- if they are convicted.

Sgt. Janek Pawek Pietrzak, 24, and his 26-year-old wife, Quiana Faye Jenkins-Pietrzak, were both gagged and shot in the head multiple times, and she was also sexually assaulted with a vibrator, authorities said.

Authorities conducted a welfare check when employers of both victims notified sheriff's deputies that the husband and wife had failed to show up for work. Their bodies were found Oct. 25 in the family room of their two-story home on Bermuda Avenue.

Pietrzak worked out of Camp Pendleton, like the defendants, and his wife worked for the Riverside County Department of Public Health.

According to court papers, the men all admitted going to the couple's home to rob them, and Miller "further admitted that he forced entry into the residence by pointing a shotgun at Janek Pietrzak," according to a declaration filed by sheriff's investigator Gary LeClair in support of an arrest warrant.

Miller fingered John as the alleged shooter, according to the document.

In the Marine barracks where John lived, investigators found shoes matching an impression found on the sergeant's body, according to court papers.

Investigators also found shoes in Cox's barracks with a tread that matched an impression left at the crime scene, and property that came from the Pietrzak home was found in Sykes' possession, the declaration states.

Pietrzak, who was originally from Brooklyn, was part of the 3rd Marine Aircraft Wing at the base near Oceanside and had served in Iraq from July 2005 to February 2006.

According to a Camp Pendleton spokesman, Cox and Miller worked in the sergeant's squadron, and John worked in the same aircraft group as Pietrzak, Cox and Miller. Sykes worked in the First Marine Division as an administrative clerk.