LOS ANGELES, Oct. 30 – Two psychiatrists said Thursday that in their opinions, a key prosecution witness is competent to testify in the Tate-LaBianca murder trial.

Drs. Blake Skrdla and Earl C. Deering testified that they think Diane Lake, 17, a former member of the Charles Manson “family,” could understand a conversation she supposedly had in September, 1969.

The teenager reportedly will say — if permitted to testify before the jury — that last year at Willow Springs in Death Valley defendant Leslie Van Houten admitted helping in the murders of Leno and Rosemary LaBianca.

Miss Lake’s testimony may be crucial to continued prosecution of the slender, dark-haired Miss Van Houten on two counts of murder and a charge of conspiracy to commit murder.

Earlier, Miss Van Houten was connected with the LaBianca murders through the testimony of Linda Kasabian, the state’s star witness.

But, if the jury finds that Mrs. Kasabian was an accomplice to the murders, her testimony could not be used exclusively to convict Miss Van Houten.

Legally, it is necessary to corroborate the testimony of an accomplice.

Without Miss Lake’s testimony, the prosecution might not be able to do that, and Miss Van Houten would be freed before the defense begins its case.

Thursday’s hearing, held out of the presence of the jury, was to determine whether Miss Lake, nicknamed ‘Snake” and also known as Diane Bluestein, is competent to testify.

Miss Lake was arrested by Inyo County authorities Oct. 12, 1969, in a Death Valley roundup of Manson family members on auto theft and arson charges.

Because of her unusual behavior, the teenager — then 16 — was committed to Patton State Hospital in San Bernardino Jan. 10. She was released Aug. 30.

In cross-examination of Skrdla and Deering Thursday, the defense produced hospital diagnoses of Miss Lake as a schizophrenic requiring long-term care.

One report described the young woman as “autistic, alogical and confabulated.”

However, both Skrdla and Deering testified they think Miss Lake’s condition was drug-induced and that she was not a true schizophrenic.

Miss Van Hoten’s attorney, Ronald Hughes, subpoenaed seven Patton State Hospital employees, including two doctors, to testify today when the hearing resumes.

By JOHN KENDALL