WORTHINGTON — On the fifth day of the criminal trial of Christopher Kruse in the murder of Janette Pigman-Kruse, jury members heard Thursday from Bureau of Criminal Apprehension forensic scientists who examined firearms, DNA and fingerprints found at the crime scene.

BCA firearm and toolmark examiner Lisa Kinsella was questioned for nearly four hours.

Kinsella explained there are certain characteristics of fired ammunition that can help determine a specific firearm that shot the particular shells. When a firearm examiner has surveyed an empty shell, one of three conclusions is reached: identification (the shell was shot from the firearm in question), elimination (the shell was not shot from the firearm in question) or inconclusive (the examiner is not sure).

If the conclusion is identification, it is BCA policy that a peer will verify the findings. If the examiners can't agree on a conclusion, the more conservative one is reported.

Regardless of the original conclusion, each case undergoes a technical review by a peer and an administrative review by a supervisor.

Relating to the Kruse case, Kinsella examined eight firearms (seven of which were .12-gauge shotguns) taken from the Kruse house and shop, the two empty shotgun shells found at the scene, the projectile fragments discovered in the pillows and slug wadding lifted from the bedroom floor. She looked at the items personally and also made some silicon castings to get a better microscopic view.

Two types of markings — firing marks and cycling marks — help establish whether a shell was shot from a specific firearm. Firing marks include the firing pin impression and breech face marks impressed on the primer (the metal base of the shell). Cycling marks occur when a shell is moved through the action of the gun, such as extractor (a hook that moves the shell out of the chamber after it has been fired) marks and shell stop (a metal piece that keeps a shell in the magazine and moves out of the way when shell enters the chamber) marks.

To study the lead fragments and wadding, Kinsella compared them with dissected ammunition kept in the BCA lab. She found that the lead fragments were consistent with Winchester Super X ammunition, and the wads matched with the Winchester brand over powder shells.

To begin looking at the shells, she first fired two test shots out of each of the firearms that had commonalities with the ammunition (.12-gauges) and were functional. She made sure the test shots had comparable markings with each other, and then looked at them under a microscope next to the shells found at the scene.

Kinsella also test-cycled two shot shells through the action of each firearm tested, compared the test-cycled shells with each other and then to the spent shells from the scene.

"I can't manufacture a conclusion because of some external desire or information," Kinsella told prosecutors. In fact, she did not have any details about the circumstances or the case when she did her examination in the fall of 2015.

With just two test fires (the bare minimum required by the BCA), Kinsella didn't believe the shells from the scene were an identifiable match with the proposed murder weapon, a .12-gauge found in Kruse's shop. On technical review, a peer recommended that Kinsella do some more test fires to have more information for comparison.

After two more test fires, Kinsella found there was enough agreement between the test fired shells from the proposed murder weapon and the shells from the scene to report a conclusion of identification. This result was also verified by a peer and underwent an additional technical review. Kinsella said she was confident that the .12-gauge found in Kruse's shop was the gun that fired the shells found at the crime scene.

The defense argued that although there are prescribed procedural steps, Kinsella's testing had some subjective elements, such as the amount of lighting and magnification used. They also reported concern that Kinsella could not give a numerical level of certainty.

"The only way to know for certain would be to examine every firearm," said defense attorney Steven Groschen.

Counsel on both sides of the case also spoke with Allison Dolenc, a DNA analyst who formerly worked at the BCA and ran DNA testing on items found at the scene of the crime.

Investigators collected the clothing Kruse was wearing at the time of his wife's murder. Dolenc identified small stains on his shirt as blood, and compared the DNA found there against DNA samples from each member of the Kruse household. She found that the blood belonged to Janette-Pigman Kruse.

Dolenc could not find enough DNA on the recovered shotgun shells to test them. The proposed murder weapon had enough DNA to test, but not enough to draw any conclusions.

BCA latent print examiner Jennifer Kostroski also answered attorneys' questions. She reported that she examined a total of eight latent prints from the scene, with five taken from the broken window in the basement bedroom belonging to Isaac Kruse. Four of the five were identified as Isaac's prints, with the fifth inconclusive. One of the seven Kruse shotguns had prints on it, but not the one prosecutors believe is the murder weapon. The remaining four fingerprints remain unidentified.

At the end of the day, the prosecution had begun to interview Nobles County Sheriff's Office Detective Sgt. Lonnie Roloff, who helped investigate the case. They will continue with his testimony Friday morning.