The murder trial of Harold Henthorn, the man who is accused of pushing his wife off a cliff to her death at a national park for her insurance money, began on Tuesday at a U.S. federal court. Henthorn, 59, is charged with first-degree murder for the death of Toni Henthorn, who plunged 120 feet from the top of a cliff at Rocky Mountain National Park, located 65 miles from Denver, according to Reuters.

During the opening trial, prosecutors alleged that Henthorn may have also killed his first wife in a similar fashion 20 years earlier. Sandra Lynn Henthorn was crushed by a car after it slipped from a jack while changing a flat tire in 1995, Assistant U.S. Attorney Suneeta Hazra said.

Prosecutors also focused on Henthorn's inconsistencies regarding the lead-up to the fall and his reaction. For one, he claimed that he called 911 about 45 minutes after his wife stumbled because he got preoccupied with their daughter's baby-sitter's text message. However, his phone records showed otherwise.

Henthorn was also unable to explain to the authorities why he had a map of a park with an "X" drawn on the same spot where his wife fell, authorities revealed, according to CBS Denver.

The Henthorns were celebrating their 12th wedding anniversary at the park in September of 2012. Prosecutors argued that Henthorn had plotted the killing carefully, searching around the trail nine times before he took his wife along with him.

His wife stopped to take a photo as they were strolling around the trail. Not long after, she toppled down the ledge face first, autopsy reports revealed, HNGN previously reported.