Bills, 21, of Dayton, is facing two counts of homicide by vehicle by reckless driving in connection with the deaths of David Castenson, 56, of Harcourt, and his mother, Velma Castenson, 85, of Dayton.

The accident happened at Samson Avenue and Iowa Highway 175 in Webster County.

Prosecutors are alleging that Bills was texting at the time of the accident, which happened while he was on his way to work.

During Bills’ bench trial in Webster County District Court Tuesday, Michaela Wenke, 19, of Eldora, testified that she was dating Bills at the time of the accident.

-Messenger photo by Hans Madsen Michaela Wenke, of Eldora, testifies in Webster County District Court Tuesday afternoon during the homicide by vehicle by reckless driving trial of Colten Bills, 21, of Dayton. Wenke and Bills were texting each other during the day of the accident.

Wenke said she was still in high school on May 8, 2015, and had been texting Bills about her classwork.

It was common for them to send about 200 text messages between each other every day, she said.

Wenke said the two had sent multiple texts back and forth until 8:43:16 a.m., when she sent him a text that Bills didn’t reply to.

He finally responded nearly 30 minutes later, at 9:22:53 a.m., telling Wenke that he had been involved in an accident and was going to the hospital.

Later that day, Wenke said she texted Bills and asked if he had been texting her while driving.

-Messenger photo by Hans Madsen Iowa State Patrol Trooper Mark Anderson, a technical investigator and accident reconstructionist, goes over a map of the accident area during the homicide by vehicle by reckless driving trial of Colten Bills, 21, of Dayton in Webster County District Court. Bills’ defense attorney, Charles Kenville, is at left.

“Why did you do that?” Coleman McAllister, assistant Iowa attorney general, asked Wenke during court.

“‘Cause I thought that the time where he stopped texting me, maybe that’s why it happened,” Wenke said.

She said Bills didn’t answer her question.

“I know that he was texting me, but I figured he was already at work just because of the time,” Wenke said.

“So when you asked him if he’d been texting before the collision, did he answer?” McAllister asked.

-Messenger photo by Hans Madsen Assistant Iowa Attorney General Coleman McAllister asks a question Tuesday afternoon during the trial. Webster County Attorney Jennifer Benson, listens at right.

“No,” Wenke replied.

The accident was reported to law enforcement by James Frank, of Stratford.

Frank, the owner of Stratford Gravel, said he was driving his truck to Humboldt when he drove past the accident. He said he stopped to see if anybody needed help and called 911 when he saw the Castensons unconscious in their car.

The Hamilton County Communications Center, which accepted Frank’s call, logged the exact time the report came in as 8:44:47 a.m.

Using the time of the report, Daniel McGehee, an expert prosecution witness who specializes in studying driver attention and distraction, constructed a timeline of how he believes the events of that day unfolded.

McGehee, who is also the director of the National Advanced Driving Simulator Laboratories, used the accident report from Iowa State Patrol Trooper Mark Anderson, who is also a technical investigator and accident reconstructionist, as well as Bills’ phone records to piece together how he believed the accident happened.

In his testimony, McGehee said he believes that Bills was distracted by sending and receiving text messages, causing him to run the stop sign and into the Castenson’s car.

McGehee specifically cited the text messages on Bills’ phone as evidence for supporting his theory.

“He responded, and based on this timeline and analysis relative to the crash, shows he was driving the car during this part of the drive,” McGehee said. “The 19-character response was typed out back to Ms. Wenke and sent.”

He added that Bills seemed to be paying attention to the text conversation.

“The message is fairly lengthy in the context of school,” he said. “The answer appears to acknowledge what she’s been saying.”

However, Charles Kenville, one of Bills’ defense attorneys, argued that the timeline doesn’t prove that Bills was texting while driving, since nobody knows exactly when the accident happened.

There were no eyewitnesses to the crash.

Under cross-examination, McGehee revealed that he didn’t know the exact time for the 911 call wasn’t 8:44:47 a.m. until Monday. On his timeline, he had the time of the 911 call as 8:44 a.m.

“The timing’s really important on this, isn’t it?” Kenville asked McGehee.

“Absolutely, and it’s where I can’t find any scenario where he’s not on the phone during these last calls,” McGehee replied.

Kenville also argued that there’s no way to prove how long Bills spent texting or if he was even texting while driving at all.

“How fast does Colten text?” Kenville asked.

“I don’t know,” McGehee replied.

“Does he use one hand or two to text?

“I don’t know.”

“Did he use one hand or two hands that day?”

“I don’t know.”

“Did he have to unlock his phone?”

“I don’t know.”

Kenville said it’s possible that Bills may have been distracted by something else. The pickup truck he was driving had manual transmission, which Bills’ father, David Bills, testified his son only learned to drive about two months before the crash.

Colten Bills did not testify Tuesday, and the defense did not call any witnesses.

Other prosecution witnesses included Webster County Sheriff’s Sgt. Tony Walter, who was the first law enforcement officer on scene, as well as Sheriff’s Lt. Kevin Kruse and Iowa State Patrol Trooper Jesse Davenport.

During his opening statement, Derek Johnson, another of Bills’ attorneys, said state law does not allow for a conviction of homicide by vehicle by texting. He said the state does not classify texting as reckless driving.

“This is a tragic case,” Johnson said. “Mr. and Mrs. Castenson did not deserve to die. They should be alive today. It is tragic, but the case should be before the Legislature to do something about the texting laws.”

“Putting a young man and having him face these kinds of charges is not the appropriate way to get laws passed,” he added.

Chief District Court Judge Kurt Wilke, who presided over Bills’ trial, said he will allow both prosecution and defense seven days to write their briefs on the case. He will schedule a hearing once he has made a decision.

Webster County Attorney Jennifer Benson also represented the state in Tuesday’s hearing.

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