LA CROSSE, Wis. -- The lead investigator in the Eric Koula double homicide trial testifies he thinks the defendant misled investigators.

Two key investigators took the witness stand Monday as week two of the Eric Koula trial begins.

The West Salem man is accused of killing his parents, Dennis and Merna Koula, over money two years ago in their home in Barre Mills.

John Christopherson, the lead investigator of this case from the Department of Criminal Investigation, testified he began to be suspicious of Eric Koula shortly after his parents were slain.

He said Eric Koula laid out a detailed timeline for investigators of where he was the day his parents were shot to death and where he was the day after, but at no point did he mention the $50,000 check signed in his father's name, dated the day of the killings, and deposited by Eric Koula the day after.

Christopherson also testified that, unlike other members of the Koula family, Eric Koula never asked if there were any suspects or how the investigation was going.

He said his regular interviews with Eric Koula eventually turned into an “interrogation.”

"I became more accusatory toward him in questioning the lies or the inconsistencies in his previous statements,” said Christopherson. “I wanted to challenge him on the information that he had been providing us. And we were at a point in the investigation that we believed that he was the individual responsible for the death of his parents."

Forensic document examiner Jane Lewis testified Monday that the check Eric Koula deposited the day after his parents' deaths was forged.

She compared the handwriting on that check to two other checks known to be written by Dennis Koula.

"The person who wrote this was trying to make it look like Dennis Koula's genuine signature, but did not do a good job,” said Lewis.

There are several ways she said she can tell the check was not actually written by Eric Koula's father. She said the signature was retouched. The “A” in Koula was retraced, which is unusual in a normal signature. Plus, the "K" in Koula was constructed differently.

"The fluency of that signature -- the maker of check signature -- was so different, and then also design changes in the letters were so different that it was a classic simulation," said Lewis.

The defense has previously said they have documents proving Eric Koula had his father's permission to sign his father's checks because of a business arrangement between the two of them.

The prosecution is expected to rest its case late Wednesday or early Thursday.

Koula has pleaded not guilty. He faces life in prison if convicted.

The trial is expected to continue late into June.