Watson arrived in Los Angeles from Melbourne, Australia, on Thanksgiving morning. He was already convicted of manslaughter in Australia for the death of his wife while scuba diving on their honeymoon at the Great Barrier Reef in 2003.
Watson was dubbed the "Honeymoon Killer" by the Australian media.
Australian prosecutors initially accused Watson of purposely drowning 26-year-old Tina Watson to collect on her life insurance policy. Watson eventually pleaded guilty to lesser charges and was released after serving 18 months in prison, which outraged the victim's family.
"This is not justice," said the victim's father, Tommy Thomas. "We believe that Gabe Watson murdered our daughter. We'll continue to believe that."
Alabama's attorney general alleges that Watson planned the murder in Alabama, giving the U.S. jurisdiction in the case. He also said there are no international standards on double jeopardy to keep Alabama from prosecuting Watson again.
Australia, which has no death penalty, released Watson after U.S. officials promised he would not face a death sentence.