Fairbanks jurors got a step-by-step look at the investigation into 16-year-old David Grunwald's murder during the ninth day of Bradley Renfro's trial Monday. 

Lead investigator, Alaska State Trooper Sgt. Tony Wegrzyn, detailed every day for the jury, starting Nov. 13, 2016 when Grunwald went missing to Dec. 2, 2016 when one of the four teens charged in his murder led troopers to the body.

"I ran this like a murder investigation with the hope that we would find David mad at his parents and not coming out," Wegrzyn said. 

Alaska State Trooper Sgt. Tony Wegrzyn testifies during Bradley Renfro's trial. (Daniella Rivera / KTVA)

He spent hours on the witness stand, sifting through the pages of a thick binder of reports, explaining how troopers identified Renfro, now 18, as a suspect once it became clear they were dealing with more than a missing person case. 

Erick Almandinger was their first suspect because Grunwald had mentioned his name to his girlfriend. Then the cell phone used to call a cab from the scene of Grunwald's burned Ford Bronco led investigators to Dominic Johnson.

Both Almandinger and Johnson have been convicted of the murder by juries. 

None of the teens were identified by the driver of the cab. He didn't feel comfortable picking anyone out of a lineup, Wegrzyn said.  

"His explanation was essentially that he’s a cab driver, he sees a lot of fares, it was dark that night. This one didn’t stick out to him other than that it was three young adult males he thought not dressed for the weather," he testified. 

But Renfro's name had already surfaced and troopers decided to speak with him at a traffic stop. The first interview, in which he claimed he was too drunk to remember anything but then admitted he was in the cab, solidified Renfro as the third suspect.

The chance to cooperate was there for the taking. Troopers wanted to find Grunwald so badly they would have welcomed help from any one of the three teens. 

If one of them would lead them to Grunwald's body, "it didn’t matter who it was," Wegrzyn said.

In a second interview with Renfro, troopers thought they were making progress. He continued to deny involvement, then made a statement to the effect that, in the worst case scenario, he had burned the Bronco. It was a turning point, Wegrzyn said. 

Troopers applied for a glass warrant, provided Renfro with a phone and let him leave. He was supposed to record his communication with the other suspects and report back to troopers but Wegrzyn said nothing came of that effort. 

Johnson, with an attorney, led troopers to Grunwald's body in December that year, with an understanding that the act would mitigate a future prison sentence. 

Palmer District Attorney Roman Kalytiak shows Dr. Kenneth Gallagher a firearm and asks him whether it could have been used to assault Grunwald. (Daniella Rivera / KTVA)

Later in the afternoon, the jury heard from medical examiner Dr. Ken Gallagher and viewed autopsy photos. The evidence confirms Grunwald was beaten and then executed with a gunshot wound to the head. 

Grunwald's parents did not attend Gallagher's testimony, knowing the photos would be shown. 

Renfro looked at the photos, looked down and appeared to take notes during that part of the trial. 

Prosecutors plan to play Renfro's second interview with troopers for the jury on Tuesday.   

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