San Mateo Man Charged With Murder Enters Not Guilty by Reason of Insanity Plea

Mark Mechikoff, 39, of Pacifica, pleaded both not guilty and not guilty by reason of insanity to first-degree murder, San Mateo County District Attorney Steve Wagstaffe announced, in a case that centers on allegations he stabbed Claribel Estrella to death on her kitchen floor and then posted a Facebook video showing her still alive and covered in blood.

Wagstaffe said the trial will unfold in two phases: jurors will first consider the standard not guilty plea, and if they return a guilty verdict, the case will proceed to a separate trial on the insanity claim. Two court-appointed doctors are evaluating Mechikoff's sanity, with their reports due in court March 11 and a jury trial set for Aug. 28.

The dual pleas come after a prolonged competency dispute. Mechikoff was initially found not competent to stand trial last year by court-appointed doctors. That finding was later reaffirmed at Napa State Hospital, where doctors concluded that treatment and medication were unlikely to restore him to a level of competency that would make him eligible for trial, Wagstaffe said.

The legal threshold for an insanity defense in California is a demanding one, as illustrated by cases elsewhere in the region. In San Carlos, defendant Jose Rafael Solano Landaeta withdrew an insanity plea just as jury selection began in his murder case, pivoting instead to an imperfect self-defense theory. Wagstaffe, who also prosecuted that case, said the shift was telling: "They obviously assessed the situation and decided that the plea of not guilty by reason of insanity is not one they felt they could carry. It simplifies the trial and I'm glad for that."

Defense attorneys in a separate San Mateo County case had similarly struggled to prove that a diagnosed mental illness was actively affecting their client at the specific moment of the alleged crime, a distinction that courts require and prosecutors routinely exploit.

Mechikoff's case now waits on the two doctors' sanity evaluations before the August trial date.