Greg Fisher | CBS News 48 Hours

Following last week’s testimonies including archeologists and cadaver dog handlers, forensic specialist Shelby Liddell took the stand on Wednesday, describing the excavation process which ensued at Ruben Flores’ home, 710 White Ct., in March and April 2021. 

Liddell has been a forensic specialist with the San Luis Obispo County Sheriff’s Department for “close to four years” and logged more than 330 hours in crime scene investigation training, partially through the FBI, the Department of Justice and Cal State Long Beach. 

The excavation process started on March 15, where Liddell and her team set up a grid, split it into quadrants and photographed it.

“We slowly… will scrape off the soil and collect it,” Liddell said.

Liddell told prosecutor Christopher Peuvrelle that her team used gloves whenever they worked on the scene. Each tool used to dig was hosed down with water, antiseptic spray and dried in between excavations. 

Liddell and her team were looking for notable items of evidence on the Kristin Smart case.

The first excavation began on March 16, where Liddell and her team found staining in the soil under all four quadrants of an area labeled Grid One.

Greg Fisher | CBS News 48 Hours

Grid One was underneath the deck of the home, the same place where two human remains detection dogs exhibited a change in behavior consistent with being in their target scent (of human remains) the day prior. 

“Close to around 2 feet down we started noticing some changes in the color of the soil that looked like stains,” Liddell said.

The stain was lighter than the soil around it with a darker border edge. 

Peuvrelle showed a photo to the jury of the soil in Grid One on Sept. 1, which revealed an irregular pattern in the soil in the shape of a ring. Cindy Arrington, an archeologist who was at the search of 710 White Ct. with Liddell, indicated that the pattern was outlining where fluids had leaked out into the soil at some point.

Peuvrelle asked Arrington on Sept. 1 what conclusions she could draw from the staining. She said it showed “fluid had leaked, likely from decomposition.” 

“We have an irregular pattern where the soil is darker than the soil within it and out of it,” Arrington said. This fluid has leaked into the soil slowly over time — not quickly, or the lines would be thicker.”

Liddell said on Wednesday that her team collected a soil sample from that area on March 16.

“We asked the detectives to pause, and I collected a sample from the interior part of the staining using a trowel,” Liddell said.

Liddell and her team collected various soil samples throughout the search, which were sent off to testing.

Continuing to dig, Liddell “observed more staining” which “wasn’t continuous.” The stains found were from different depths and places in the soil.

Liddell said on Wednesday that she did not find any animal remains during the excavations.

The Flores’ deck was removed in April in order to investigate a separate area under it. The archeologists theorized that the “fluids” they found on Grid One could be leaking from there, so the police ordered the removal of the deck.

During his opening statement in July, Ruben Flores’ attorney Harold Mesick said that the space is too small to bury a body– a 6’1” body.

With the deck removed, detectives were able to excavate places they hadn’t been able to reach before. Before excavating, the team laid out quadrants again. Excavation underneath the deck on April 13 and 14 revealed more staining. 

Peuvrelle showed Liddell photos of the staining, with Liddell identifying the components of each stain.

Detectives found staining across each quadrant of the new grid.

The first sample from quadrant A showed a stain, with a follow up sample of quadrant B having “multiple areas of staining.” Detectives took more samples from both these quadrants. On Wednesday, Liddell noted the fourth sample from quadrant B had a “noticeable darker, thicker area.”

During the search in April, detectives re-dug the hole they excavated at Grid One– the soil where Arrington described that fluid had leaked onto.

During his cross examination, Paul Flores’ attorney, Robert Sanger, questioned how the stain appeared in the soil in the same place in April after detectives dug out the area in March and then re-deposited the soil to be dug out again in April. 

He asked Liddell if it was a possibility that the stain was deposited between March and April, which Liddell said was beyond her area of expertise.

In quadrant E of this area, Liddell found that the staining “went up the sides of both of the walls on either side.” The walls Liddell described contained both the walls of the house and of the deck.

Eventually, detectives hit a point where it was “extremely difficult to dig.” They never digged beyond. 

During his cross examination, Mesick asked Liddell about this.

“Do you think you might’ve hit concrete at 4 feet?”

“It appeared more organic to me because we were able to break it apart. But that is not my expertise,” she said.

Liddell said that it was her job to photograph and collect potential evidence from the excavations, but she maintained that she did not receive the results and that she is not an expert in soil.

After completing the excavation underneath the deck, detectives put the dirt back into place. 

During the searches in both March and April, Liddell saw two trailers at the Flores’ home — one a cargo and the other a travel trailer, including a bed.

Liddell described the cargo trailer as “cluttered,” noting that only one person could fit inside. 

Detectives took the reacted 2.5 by 3 feet plywood piece of the trailer, which belonged to Susan Flores’ boyfriend, Mike McConville, to the lab for testing. 

“That general area had a positive ‘Bluestar’ reaction,” said Liddell on Wednesday.

Bluestar is a chemical that reacts to the iron in blood, which forensic analysts commonly use to detect human blood in samples. The chemical also reacts to chlorine-bleach, in which it will glow a different color– a “white-blue.” 

“You’re aware this came back as not blood?” Sanger asked during his cross examination.

“I have not been told that that is not blood,” Liddell said.

Sanger also asked Liddell about excavations she did in Huasna and Arroyo Grande related to the case. He asked her if she ever found any evidence as a result of those excavations.

“None that were associated with Kristin Smart, no,” said Liddell.

Sanger later switched to asking Liddell about the prosecution’s theory that Paul and Ruben Flores buried Smart under the deck and removed her body from it at one point.

“If the theory was that somebody dug a grave and put a body in it and took the body out and it left a stain, the stain would be below the level of the body,” Sanger said. 

The shallowest signs of staining were around 2 feet underground, while the deepest were around 4 feet.

Peuvrelle objected to this, which Judge Jenifer O’Keefe sustained.

“You’ve been talking about a stain,” continued Sanger. “What kind of a stain is it? Why are you calling it a stain?”

“It’s a clear discoloration,” Liddell said, who maintained throughout her cross examination that she is not an expert in soil.

Sanger also asked Liddell about a statement she made during the preliminary hearings in 2021, where she said that it did not appear that the staining in the soil had been disturbed.

Liddell clarified this on Wednesday, saying that she had taken Sanger “too literally” last year and that she had thought that he was asking about the stain itself rather than the soil around it. The stain itself hadn’t been disturbed, but the soil around it had.

The trial will resume Thursday morning. According to Judge O Keefe, it will be a “very full day of testimony tomorrow.”