Three members of an alleged bondage ring have appeared in court on charges of murder, kidnapping, torture, attempted sexual battery and conspiracy, following a woman's violent death after being convinced to go on a dinner cruise with her neighbour.

22-year-old Brittany Killgore had reluctantly agreed to go on a date with Louis Perez after she asked for his help moving furniture out of her flat in San Diego, California.

She is said to have indicated her hesitance over the date to Perez's roomate, 37-year-old Dorothy Maraglino, but was allegedly convinced by her that all would be OK.

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Superior Court Judge K. Michael Kirkman said evidence suggested that the former-wife of a serving Marine was in fact the innocent victim of a premeditated plan by Perez's bondage “slave”, 25-year-old Jessica Lopez, who was convinced she would steal her “master” away.

Deputy district attorney Patrick Espinoza said that in the days before Ms Killgore's death, Lopez had told other members of San Diego's bondage community that she planned to launch an attack on her.

“We know from the evidence that that unsuspecting prey was Brittany Killgore,” Espinoza said.

Despite the discovery of Ms Killgore's blood in Perez's car the day after her disappearance, defence attorneys argued that physical evidence was lacking.

Lopez's attorney, Sloan Ostbye, called her client “the perfect slave” in the triangle and said her role explained why Lopez authored a handwritten letter taking full blame for Ms Killgore's death.

In the letter, Lopez claimed she killed Ms Killgore out of fear that the woman would steal Perez, whom she described as her “master.”

“It's not a confession letter, it's an exoneration letter ... to help mistress and master,” Ostbye said.

Ms Killgore disappeared in April 2012 after borrowing a purple evening gown for the cruise, according to prosecutors. Her nude, strangled body was four days later near Lake Skinner, north of San Diego.

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Yesterday, the lead detective testified that a document attributed to Maraglino identifies her as a participant in a beating and asphyxiation.

“We had the best of intentions and any injury or loss of life should be considered an accident,” read the document recovered from a CD.

Detective Brian Patterson, who read the document aloud, said investigators also found whips, paddles, videos and other evidence of a sex bondage activity at Maraglino's home in Fallbrook, north of San Diego.

Another San Diego County sheriff's detective, Daniel Pierce, testified that cellphone towers traced Lopez's phone to the area where Ms Killgore's body was found. The phone was located in the area shortly before 4am, several hours after Ms Killgore disappeared.

Last week, Elizabeth Hernandez, who was identified in court as the victim's best friend, testified that she and Ms Killgore became acquainted with the defendants in 2011 after she responded to an advert selling a fertility monitor on a website used by military families.

She said they used to socialize with them but never participated in their alternative lifestyle in which Perez played the master, Maraglino was the mistress and Lopez was the slave.

Ms Hernandez testified that she and Ms Killgore had a falling out in 2012 as the victim prepared to divorce her husband, Lance Corporal Cory Killgore, who was serving in Afghanistan at the time of his wife's death.

She said Brittany Killgore started dating Ms Hernandez's brother, and they started referring to her as “the disease.”

Perez told investigators he dropped off Ms Killgore in downtown San Diego's bustling Gaslamp District after their date, but investigators concluded that he lied about his whereabouts and stayed in Fallbrook.

Perez was the first to be arrested on suspicion of possessing a stolen assault rifle and was later charged with murder. Lopez was arrested two days later at a San Diego hotel where authorities said she was discovered with self-inflicted cuts.

The trial continues.