SANTA ANA (AP) — Two convicted sex offenders have pleaded not guilty to the rape and murder of four California women while the men were wearing GPS tracking monitors.

Susan Kang Schroeder, chief of staff at the Orange County district attorney’s office, says 28-year-old Franc Cano and 45-year-old Steven Dean Gordon entered the pleas Wednesday.

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The men were indicted earlier this month on charges of murder with special circumstances and rape.

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Cano’s lawyer, Houman Fakhimi, declined immediate comment. A message was left for Gordon’s lawyer.

Prosecutors say the men worked together to sexually assault and kill four women since last fall while wearing tracking devices ordered after prior sex crimes. Authorities say the monitoring systems helped investigators link the pair to the killings after one woman’s body was found at a trash sorting plant.

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