TWO ADULT FEMALES WERE ARRESTED IN CONNECTION WITH THE MURDER OF AN ADULT MALE IN SAN DIEGO, CALIF. FINGERPRINTS OF ONE SUSPECT WERE FOUND IN THE MURDER ROOM, BUT NO PHYSICAL EVIDENCE PLACED THE SECOND SUSPECT AT THE SITE. ONE OF THE DETECTIVES FOUND A WAD OF CHEWING GUM ON A DRESSER IN THE ROOM, PRESERVED THE EVIDENCE, AND BROUGHT IT TO THE CRIME LABORATORY. DENTAL IMPRESSIONS WERE OBTAINED FROM THE VICTIM AND EACH OF THE SUSPECTS. THE IMPRESSIONS CLOSELY MATCHED THOSE OF THE INCISORS OF THE SECOND SUSPECT. CHEMICAL ANALYSIS SHOWED THAT THE TRACES OF SALIVA ON THE GUM WERE DEPOSITED BY AN INDIVIDUAL WITH BLOOD TYPE AB. (ABOUT 80 PERCENT OF THE POPULATION CONSISTS OF 'SECRETORS,' WHO REVEAL THEIR BLOOD TYPE IN THEIR SALIVA, PERSPIRATION, TEARS, AND IN THE CASE OF MEN, SEMINAL FLUID.) THE SECOND SUSPECT ALSO HAD TYPE AB BLOOD. SINCE THIS BLOOD TYPE IS FOUND IN ONLY 4 PERCENT OF THE POPULATION OF THE UNITED STATES, THE PHYSICAL IDENTIFICATION WAS CONSIDERED SOUND. BOTH SUSPECTS ENTERED A GUILTY PLEA. PHOTOGRAPHS ILLUSTRATE THE DENTAL MODELS OBTAINED. TABLES DESCRIBE THE FREQUENCY OF BLOOD TYPES IN THE U.S. AND A COMPARISON OF THE SALIVARY AND BLOOD TYPES OF THE TWO SUSPECTS. IT IS ALSO SUGGESTED THAT SALIVA FOUND ON BITTEN FOOD AND BEVERAGE CONTAINERS MAY BE USED TO DETERMINE BLOOD TYPES OF SUSPECTS. (GLR)