Gardner had been convicted in 2000 of molesting a 13-year-old female neighbor. He spent five years in prison and completed his parole in 2008, although it was determined that he had violated the terms of his parole seven times, including living too close to a school in 2007. Gardner was also investigated by his parole officer for possession of marijuana, though this incident was later dismissed. Gardner was also being tracked by a GPS anklet up until four months before the murder of Amber Dubois. Gardner totalled 168 parole violations while wearing the anklet. According to GPS data, Gardner spent time in close proximity to several schools, in front of a daycare center, on prison grounds, and in remote locations where the remains of Amber Dubois would later be discovered.
Murders
Gardner's first murder victim was 14-year-old Amber Dubois, who disappeared in February 2009. Her skeletal remains were later recovered by police in March 2010, after the police had questioned Gardner about her murder. Gardner had been arrested on February 28, 2010, in the Del Dios district of Escondido, California, when his DNA matched a DNA sample taken from the discarded clothing of Chelsea King, a senior from nearby Poway High School. King had disappeared on February 25, 2010, while she was jogging in the early evening at the Rancho Bernardo Community Park, near Lake Hodges. FBI divers found her body five days later buried in a shallow grave on the southeast corner of the lake's inlet, where some of her clothes had been found. DNA evidence from King's clothing, along with a December 2009 attempted attack on a female jogger who managed to fight him off, led Escondido and San Diego police to patrol the area for a man fitting Gardner's description. He was arrested on February 28 at a bar and restaurant in Del Dios, at the western shore of Lake Hodges in Escondido. A witness has indicated that Gardner returned to the park subsequent to King's disappearance.
Guilty pleas
On April 16, 2010, Gardner pleaded guilty to the murder and rape of both Dubois and King in 2010, after the prosecutors agreed not to seek the death penalty. He admitted to kidnapping, raping, and stabbing Dubois. He also admitted dragging King to a remote area where he raped and strangled her, and then buried the body. In addition, Gardner also admitted and pleaded guilty to attempting to rape Candice Moncayo in December 2009, who was able to fight back and escape. Sentencing was set for June 1, 2010, although it took place on May 14, where Gardner was sentenced to two terms of life in prison without the possibility of parole. The parents of Amber and Chelsea, and the surviving victim Candice Moncayo, made impact statements prior to sentencing describing the impact Gardner's crimes had on their lives, and their determination to see to it that "Chelsea's Law"; introduced by Assemblymen Nathan Fletcher, this was signed into California state law by then-Gov. Arnold Schwarzenegger on September 9, 2010, to help prevent similar crimes in the future. During the trial, the Kings retained Michael Fell, a California criminal lawyer and former prosecutor, who specializes in representing victims under Marsy's Law, the state constitutional amendment that guarantees legal rights for victims of crime.
Sentencing
On May 14, 2010, Judge David Danielsen sentenced Gardner to life imprisonment with no possibility of parole, two terms of life imprisonment without parole for the murder and rape of Chelsea King and Amber Dubois, another term of 25 years to life for assault with attempt to commit a rape, and an additional 24 years of imprisonment for prior convictions. Since he entered the plea agreement, Gardner waived his right to appeal. Gardner is currently incarcerated at Mule Creek State Prison.
