Susan Marie Lynch was found in Sacramento, CA on July 21, 1971, beaten and covered with sand in a shallow grave, which suffocated her.
She is #22 on RG’s list, and he gives her DoD as June 19, 1971, which might be the time she went missing, but Seagull confirms, as with the article below, that the California Death Index reports her date as July 21, 1971 (although the article says she was found then, and had "been dead about three days").

I haven’t found much on Susan. The best is an article, probably from a local San Diego newspaper, which has been transcribed and copied below as part of the obituary section of the "Class of ’67" of this "Will C. Crawford High School" website: http://www.johnfry.com/pages/Obits67.html. Fortunately, they also have Susan’s High School yearbook picture.

SLAIN WOMAN DAUGHTER OF CITY RESIDENT
The body of a young woman found in a shallow grave in Sacramento on July 21 has been identified as that of Susan Marie Lynch, 22, daughter of Mrs. Ruth J. Major, of 8450 San Carlos Drive, San Diego. The identification was made Thursday by the Sacramento County coroner’s office from fingerprints. John V. Petry, a San Diego County deputy coroner, notified Mrs. Major of the death Thursday. Greenwood Mortuary here will be in charge of funeral arrangements.

FOUND BY BOYS
Boys playing in a dry creek bed in an undeveloped area of Sacramento found the body, which was on the ground but covered with sand. The body was clad in cutoff jeans, tennis shoes and a vest-type blouse.

James C. Hosand, chief deputy coroner of Sacramento, said the only injury found in an autopsy was a dislocated jaw. Tests determined the girl was alive when covered with sand and she died of suffocation, he added.

Hosand said the girl had been living in Nevada City, northwest of Sacramento, but had gone to Santa Cruz to see friends sometime in July and was hitch-hiking to Nevada City.

DEAD THREE DAYS
The girl had been dead about three days when the body was found, Hosand said, and remained unidentified as there were no fingerprints on file with the FBI or state agencies. Dental charts were circulated and news articles were published attempting to identify the body.

A Santa Cruz woman supplied Sacramento officials with Miss Lynch’s name, stating she was missing, and a thumb print from the girl’s drivers license was compared to make the identification.

Petry said Mrs. Major reported she had last heard from her daughter seven weeks ago and said the young woman had been visiting friends in Northern California. Attempts had been made to report her as a missing person, but because she was 22 no reports were taken by Northern California officers.