Suspect met Kristen Marti for sex and then cut her throat, detectives testify

Cell phone records show that an Arroyo Grande man charged with the murder of 26-year-old Kristen Marti was driving around the area where she was last seen alive weeks before her body was discovered with a slashed throat in a Prefumo Canyon creek bed, a San Luis Obispo detective testified Wednesday.

Robert William Koehler, 36, is accused of killing Marti with a knife after allegedly meeting her for paid sex in a vehicle parked in Prefumo Canyon on Jan. 9.

He has pleaded not guilty and has been in custody at San Luis Obispo County Jail without bail since May.

At a preliminary hearing Wednesday, Superior Court Judge Craig van Rooyen heard from several San Luis Obispo police investigators and a forensic toxicologist, who reportedly found drugs and alcohol in Marti’s system.

Kristen Marti
Kristen Marti

The hearing is expected to resume Thursday; at its conclusion, van Rooyen will rule whether prosecutors established probable cause to move ahead toward a murder trial.

Marti was last seen alive Jan. 9, and her body was discovered in Prefumo Canyon in late March following a large-scale search of the area.

Police announced on May 16 that they arrested Koehler, who had previously been identified as a person of interest in the case, in Minneapolis, Minnesota, after a warrant was issued when he left San Luis Obispo County with his wife. He was extradited to California after being temporarily held in the Hennepin County Jail in Minnesota.

In addition to the murder charge, the district attorney’s complaint against Koehler includes a sentencing enhancement for use of a deadly weapon — a knife — during the alleged murder. The complaint also states that Koehler has a prior felony conviction for carjacking out of Shasta County in 2005.

If convicted, Koehler faces a maximum of life in state prison.

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On Wednesday, Koehler listened attentively as Deputy District Attorney Lisa Muscari called to the stand San Luis Obispo police Officer Greg Benson, who testified that on Jan. 15, 2018, he stopped a local transient man, Nicholas Reed, whom Benson said he knew to be Marti’s boyfriend, for possessing an open container of alcohol in public.

Benson said he knew Marti and Reed were habitual heroin and methamphetamine users who either lived in local hotels or on the street, and had heard rumors that Marti supported their habits through prostitution.

Benson recalled that Reed told him he wanted to file a missing persons report after not seeing Marti for several days. Benson testified that he checked the department’s computer system and found no records indicating any officers had recently spoken to Marti.

Jacob Dinsmore, who worked as a San Luis Obispo patrol officer at the time, testified Wednesday that he took a missing persons report from Reed, who said he last received a message from Marti on Jan. 9 saying she was in Prefumo Canyon.

Reed told Dinsmore that he and another friend drove to a particular spot in Prefumo Canyon and believed they saw Marti and an unknown man inside a vehicle. Reed told Benson that he attempted to contact Marti through the window, but saw from her demeanor that she “seemed OK.”

Investigators served several search warrants in the case and in one instance examined the contents of Koehler’s phone. San Luis Obispo Det. Chris Chitty testified that Koehler communicated with Marti via an anonymous messaging app called textPlus, which requires only a valid email address to sign up.

According to Chitty, Koehler messaged Marti through the username “John Hill.” Chitty said investigators were granted access to Marti and Koehler’s textPlus accounts through a search warrant and showed the last message from John Hill to Marti read: “I’m in a red truck.”

Chitty testified that both Koehler’s textPlus account and the email address he used to establish it were deleted around 11 p.m. on Jan. 9. An IP address associated with the email address was traced to Koehler’s mother’s house, Chitty testified.

San Luis Obispo police Det. Caleb Kemp testified that detectives interviewed other men with whom Marti had allegedly met for sex, all of whom cooperated and allowed officers to view their communications with Marti, Kemp said.

Kemp said Marti was “secretive” about her “johns” and attempted to keep them away from each other, as well as from Reed and another friend, both of whom would sometimes drive Marti to meetings with clients.

Kemp testified that the first logged textPlus contact between “John Hill” and Marti was Dec. 14, 2017, and there were about 103 text messages between the two through Jan. 9. Photos sent between the two include images of a man in a Mullahey Ford mechanic shirt with “Robert” listed on the name patch.

Kemp said the nature of the communications were “drugs and sex for money,” and Marti in return asked for a “donation.”

Though Koehler in his first interviews with investigators after Marti’s disappearance eventually admitted to picking her up in San Luis Obispo on Jan. 9, he denied driving her to Prefumo Canyon, saying he instead dropped her off by a bus stop near Madonna Plaza.

But cell phone records show differently, Kemp said. He testified that Koehler’s cell phone “pinged” off several cell phone towers in the Prefumo Canyon and Avila Beach area the night of Jan. 9. After Koehler missed a phone call from his wife at about 7 p.m., there was a period of about 2.5 hours in which there was no cell phone activity before his cell phone again “pinged” near Avila Valley Drive and Highway 101.

Kemp testified that Koehler likely either powered off his phone or spent that time period in a place without cell reception.

However, detectives reviewed security camera footage from a home at the peak of Prefumo Canyon leading to See Canyon which appears to show the headlights of just one vehicle heading toward See Canyon at about 9:30 p.m. Jan. 9.

Kemp testified that Koehler began to act increasingly suspicious after search warrants were served at his various residences, including changing his phone number days after Marti’s disappearance even though he had just printed sets of business cards for his mobile auto mechanic business listing the old number.

After Koehler and his wife drove out of state in April, the couple allegedly sent a message to the wife’s mother instructing her to sell everything they had left behind.

During cross-examination, Koehler’s attorney, Trace Milan, asked Kemp whether he found it odd that neither Reed nor the other male friend who normally drove Marti to meet with clients weren’t with her that night. Kemp said no, because other witness statements described both men as heavily intoxicated that night.

Asking whether it was possible Marti suffered a fatal overdose the night of Jan. 9 and that Reed and the other friend attempted to hide her body in the Prefumo Canyon creek bed, Kemp said that was “highly improbable” based on Reed and the other man’s small statures.

When Milan asked why it was improbable that two men couldn’t move Marti’s body 40 to 50 feet to the creek bed but his client alone could, Kemp replied: “Just by looking at (Koehler’s) physical stature, he’s a pretty stout guy.”

Lastly on Wednesday, Bill Posey, a forensic toxicologist with Central Valley Toxicology who conducted a drug test on Marti, said tests found significant amounts of alcohol, cocaine, morphine, methamphetamine, and an animal tranquilizer normally used by veterinarians, in Marti’s system.

Testimony is scheduled to resume Thursday.

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Matt Fountain: 781-7909, @mattfountain1
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