The trial of the man accused of kidnapping and murdering 18-year-old Zoe Hastings opened Thursday.

Antonio Cochran, 36, is accused of kidnapping Hastings as she attempted to return a movie at a Lake Highlands pharmacy in October 2015. Prosecutors contend he was the man witnesses saw argue with Hastings and then push her into the family’s minivan. She was found stabbed in the neck the next morning in a Lake Highlands creek.

The Dallas County District Attorney's office originally planned to seek the death penalty. However, in November the DA's office announced it would reverse the decision and instead seek life imprisonment after it was discovered Cochran has an intellectual disability, which means an IQ under 70. It's against the law to execute anyone with an intellectual disability.

In his opening statements, prosecutor Pat Kirlin told jurors he would offer them a “road map” that would lead them to find Cochran guilty of murder.

He told jurors that Cochran’s DNA was found on the handle of the bloody knife found at the scene of the crime. He also told jurors that Hastings was sexually assaulted and that Cochran couldn't be excluded as a contributor of that DNA.

Paul Johnson, Cochran’s defense attorney, told jurors he would give them a “plausible explanation” for the DNA found on the knife handle. He said Cochran worked as a janitor at a movie theater and part of his job was to collect discarded items.

Hastings’ mother, Cheryl, was the first witness to take the stand.

Zoe was the eldest of Cheryl and her husband’s five children. She graduated from high school in May 2015 and was working as a lifeguard, as well as helping take care of her younger siblings, at the time of her death. Her mother said she was working to save money for a missionary trip.

On the afternoon she disappeared, Zoe left in her family’s white van to return a movie. She was also supposed to attend church but never showed. Prosecutors told jurors that records show she returned the movie at 4:42 p.m.

Meanwhile, her parents became increasingly worried when she didn't return home for dinner. They began calling and texting but couldn't reach her. Friends told them that she had not shown up to church.

“Something was wrong for sure,” Cheryl Hastings said.

About 10 p.m. that night, her parents called 911 to report her missing. When officers didn't respond within a couple of hours, her father went to a nearby patrol station and reported her missing.

During that time, her parents also began trying to find her phone using an app. At first, they couldn't get it to work. However, once they were able to, the app led them to the field where she soon learned her daughter’s van and body had been found down a steep creek embankment, Zoe's mother testified.

“They gave us the horrible news that she had passed,” she said.

Firefighter and police who took the stand testified that Hastings was found lying face down on her side. They described that her clothing was disheveled and she appeared to have been sexually assaulted. A bloody knife was found near the cliff side.

The van was nose first in the creek bed. The driver’s side door wasn't open.

Kurt Arnin, a neighbor who lives in the area, testified about a frantic man who ran up to him and reported that he found a car and a girl in the creek.

He said the man asked him to call 911 because his phone was dead. Arnin testified that he couldn't see the crime scene because the tree line and foliage obscured the view.

Arnin testified that another man and his daughter also went down there and saw the body and the van in the creek bed.

In a clear attempt to create doubt, Johnson, the defense attorney, questioned Arnin about the behavior of the unidentified man who approached him.

“He was acting in a very strange manner,” Arnin said. “He was very animated, upset.”

Johnson asked if it seemed off that the man claimed his phone was dead and therefore he couldn’t call 911.

“Everything seemed odd about this guy,” Arnin said

That man left the scene and hasn't been unidentified.

Public records show since 1998, Cochran faced charges for theft, assaulting a family member, burglary and possession of a controlled substance among other things.

In January 2015, jurors in Bowe County acquitted Cochran of raping his girlfriend’s daughter prior to moving to Dallas. Cochran is not charged with a sex crime in Hastings’ killing.

He was arrested about two weeks after Hastings’ killing.

WFAA's Marjorie Owens contributed to this report