Booking Photo (05/31/2018): Robert William Koehler, IV (DOB 03/03/1982)
Booking Photo (05/31/2018): Robert William Koehler, IV (DOB 03/03/1982)

Judge sentences Robert W. Koehler, IV to serve 56 years to life in prison for the murder of Kristen Marti

Author: District Attorney
Date: 1/31/2023 5:46:31 PM

Grover Beach resident Robert W. Koehler, IV (40) was sentenced to 56 years to life in prison today for the January 2018 brutal murder of 26-year-old Kristen Marti, who remained missing for over two months.

District Attorney Dan Dow announced today that Robert William Koehler, IV (DOB 03/03/1982) was sentenced to 56 years to life in prison for the murder of 26-year-old Kristen Marti.  

Kristen Marti went missing on January 9, 2018.  Following an exhaustive, nearly three-month search, Kristen’s remains were found in a remote area of Prefumo Canyon in San Luis Obispo on March 25, 2018. Computer forensics and other investigative tools led law enforcement to identify Koehler as the suspected murderer.

Evidence introduced at trial revealed that Koehler contacted Kristen using secretive social media apps in order to entice her to his location through his persistent offer of providing her with cocaine.  Although Kristen’s body was found in a stream buried under rocks, the forensic medical examination revealed cocaine and tiletamine, a drug that causes a human body to become immobilized, in her bloodstream. In addition, she was found to have suffered numerous knife wounds to her throat and wounds indicating that she had fought back to protect herself from the violent attack.

After an eight-week jury trial, on July 14, 2022, a San Luis Obispo County jury convicted Koehler of first-degree murder with the use of a knife.  The jury also found that Koehler had previously been convicted of carjacking, a “strike” under California’s Three Strikes law.

Today’s sentence of 56 years to life in prison, which was ordered by San Luis Obispo County Superior Court Judge Jesse Marino, was the maximum allowed based on Koehler’s conviction. 

“Today, we finally have justice for Kristen Marti five years after she was brutally murdered,” said District Attorney Dan Dow. “This defendant should spend the rest of his life in state prison and today’s sentence should make that possible. We are grateful to each of our law enforcement partners and search and rescue volunteers who never gave up searching for Kristen. Finally, we must thank the members of the jury for their service and their verdict that made today’s just sentence possible.”

At the sentencing hearing several family members, including Kristen’s mother and father, described to the Court the devastation and sadness resulting from the loss of Kristen.

This case was investigated by the San Luis Obispo Police Department with assistance from the San Luis Obispo County Sheriff's Office and the District Attorney's Bureau of Investigation and District Attorney’s Central Coast Cyber-Forensic Laboratory.  The prosecution team was led by Chief Deputy District Attorney Lisa B. Muscari who supervises sexual assault, child abuse, intimate partner violence, juvenile, and mentally disordered offender prosecutions.

To view the defendant's booking photo, click here.  To view a copy of the charging document, click here.

Please contact Assistant District Attorney Eric J. Dobroth at 805.781.5819 with any questions.