Soil samples were part of the evidence gathered at the crime scene in 2016.

Tuesday, Kathryn Sinkevitch’s first-degree murder trial entered its fourth day with the testimony of geologist forensics examiner Jody Webb from the FBI Crime Lab.

Sinkevitch is accused in the shooting death of 31-year-old Michael Agerter on Dec. 16, 2016. Agerter, her ex-boyfriend, was shot and killed in the garage of his rental home in Rancho El Dorado. The two lived separately but had an infant son together.

Webb has 21 years’ experience as an FBI geologist forensics examiner.

One of her co-workers performed soil comparison test around Agerter’s house. The co-worker could not testify Tuesday due to illness, so the FBI sent Webb who works with her and also validated these test results.

The FBI analyzed three items, a driver’s side floor mat from a vehicle believed to be used by Sinkevitch during the commission of the murder and soil from a two shoe prints at the scene of the murder.

The whole floor mat from the suspect van was sent to the FBI to be tested.

The soil samples from the floor mat and the shoe prints were compared and tests concluded the soil was different on the mat than both of the soil in the shoe prints at the scene.

The soil makeup of the two shoeprints were also different when tested by the FBI lab. Webb said it is very possible for the samples to be different and still taken in the same area.

Persecutors showed Webb a video showing a suspect wearing a dark hoodie going into the garage and walking across the areas that were tested when Agerter was murdered in the garage.

The soil samples were taken three days after the murder.

Under cross examination, defense attorney Bret Huggins noted that the soil samples don’t match and are eliminated as the source of the soil on the floor mats. Webb, the FBI analyst, agreed.

The soil samples were eliminated, she said.