CONROE, Texas -

A former Conroe Police officer is on trial this week for the manslaughter in a case that was at the center of controversy for months.

Former Sgt. Jason Blackwelder is charged with killing 19-year-old Russell Rios, a suspected shoplifter.

On Tuesday, members of both families filled the courtroom, as members of the Conroe Police Department took the stand, answering questions from the prosecution and defense.

Conroe police said Blackwelder was off duty on July 31, 2013 at Walmart, when he ran over to help capture shoplifting suspect Russell Rios. Blackwelder claimed he chased Rios out of the Walmart into the woods and Rios put him in a chokehold. At the time, Conroe police backed Blackwelder, and said the teen had attacked him.

But the prosecution says that story doesn't add up because evidence shows the bullet went through the back of Rios' head.

Today the lead detective on the case, who knows Blackwelder well, admitted he was intimidated by the fact that he was handling the investigation of a colleague who outranked him. That led investigators to tell the jury that he felt several parts of Blackwelder's story didn't add up.

A crime scene investigator also took the stand. When asked if Blackwelder in any way hindered his ability to collect forensic evidence at the scene, the crime scene investigator answered "no."

Other witnesses who took the stand Tuesday included a 911 dispatcher, as well as one of Walmart's loss prevention officers who was on the scene that night.