A Natrona County prosecutor on Monday said DNA evidence will prove a man sexually abused a 16-year-old girl in Mills three years ago.

But the defense attorney representing James Tanner said the alleged victim had reason to invent being a sexual abuse victim so her family members would send her home to Minnesota following a contentious relationship with a guardian.

Tanner is charged with third-degree sexual abuse of a minor. Monday marked the first day of his jury trial in Natrona County District Court.

Although the alleged incident took place in May 2016, prosecutors didn't pursue the case until February of this year because of a lengthy process in analyzing DNA evidence.

During opening arguments, Natrona County Assistant District Attorney Kevin Taheri said Tanner violated a family's trust when he sexually assaulted their daughter. The prosecutor told jurors that investigators found Tanner's DNA on the alleged victim's pants and undergarments.

Taheri said lab tests concluded that DNA found on the alleged victim's clothing was 100 billion times more likely to belong to her and Tanner than any other two people.

Public defender Joseph Cole is representing Tanner in the trial. Cole said Tanner is the victim of unfortunate timing.

Cole said the girl had two guardians who were both women. One lived in Minnesota while the other lived in Natrona County. The girl had been sent to live in the Casper area after running into a number of issues. At one point, the girl ran away from a treatment center in Minnesota before she was sent to live in Wyoming.

The alleged victim could have returned home under the condition of completing counseling and improving her grades, Cole said. Instead, she devised a ruse to go back to Minnesota.

According to charging documents, Bikers Against Child Abuse notified Mills police that a 16-year-old-girl had been sexually assaulted.

Cole noted during opening arguments that the alleged victim had been around Bikers Against Child Abuse for some time and that her mom is a member. The alleged victim spent enough time around BACA that "she knew how to be a victim," Cole said.

The defense attorney also told jurors that Taheri failed to mention Tanner's DNA found on the alleged victim's clothing came from skin cells, not bodily fluid.

"It was the teeniest, tiniest amount of skin cells," Cole said.

During Monday's proceedings, the alleged victim, now 20, took the stand and recalled going to a Mills residence with Tanner just before the incident.

Tanner asked the alleged victim to go with him to his mother's house to help clean it. However, during the drive over, Tanner told the victim that they weren't going to clean a house. Instead, the alleged victim testified, Tanner told her that he wanted to help her "take a break."

The girl and the victim went inside before she found herself sitting close to Tanner on a bed and began talking about drugs.

At some point, Tanner reached over and grabbed a coffee can with some sort of white powdery substance in it — the victim said Tanner told her it was "speed."

According to the alleged victim, not long after, Tanner went into a bathroom before he called for her to join him. Then, he allegedly performed a number of sex acts on the girl.

The alleged victim said she didn't tell anyone about the incident until a few hours later because she thought she wouldn't be believed. She contacted law enforcement early the next morning.

A sexual assault nurse examiner testified that the alleged victim had injuries to her genitals that were consistent with her recollection of events.

The trial, set to reconvene Tuesday morning, is expected to last at least three days.

If convicted, Tanner faces up to 15 years behind bars.