The police might never have arrested Anthony Gordon for a motel robbery here if he had not ordered personalized license plates for his Corvette. They said: "I'M EVIL.

A bystander at the robbery easily remembered the letters. Police quickly found Gordon's car, the engine still warm. He became just one more victim of California's great obsession, the personalized plate, an inadvertent aid to law enforcement, topic for sociologists and literary pastime for millions of summer vacations traveling the highways.

From JUEZA (Spanish for female judge) on U.S. Supreme Court Justice-designate Sandra D. O'Connor's Fiat to MELLIO on a white Honda at Santa Monica's Rand Corp., personalized plates have swept the Southwest, becomeing one of the most visible signs of westerners' unusual feelings about their automobiles and themselves.

Every state now offers personalized plates to motorists who will pay an extra fee, but California has the greatest number and apparently the highest percentage by far. Through June, California had issued 916,432 personalized plates, enough for nearly 7 percent of the 13.2 million passenger cars in the state.

"It's not because of any lack of security on the part of Californians, not because they have weak egos or something," said University of Southern California psychologist Jerald Jellison, a Pennsylvania native who has lived here 10 years. The automobile is so important and Californians have so much mobility, he said, "that you are coming into contact with a lot of people you don't know and you want to adverstise yourself, to say, 'This is what I am.'"

The personalized plates have brought in several million dollars for a special state fund for anti-pollution and park projects, hence the term "environmental plates" for the personalized licenses here. They also forced the state motor vehicles department to install a complicated, computerized screening of objectionable plates. The system includes administrative hearings that have overruled state objections to having plates like "PUSSY 1," which is seen on California highways.

Easterners lag in enthusiasm for personalized plates, although many states are finging them increasingly useful as a source of extra state revenue. Brenda Smalls of the D.C. bureau of motor vehicles said only 5,000 of 240,000 city license plates, 2.1 percent, are personalized. New York has 3 percent, Massachusetts 2 percent and Texas 1 percent.

Virginia has 100,000 of its 3.1 million license, 3.2 percent, somewhat personalized, but until recently it allowed only three letters plus three numbers. The state began to offer a combination of any six letters or numbers, in a new "Communiplate" plan, on May 26. Virginia charges $10 extra for the service a year, compared with $25 in California and many other states. Maryland has only 28,051 personalized plates.

Officer Emanuel Padilla, a spokesman for the California Highway Patrol, said police applaud Californians' affecton for the plates. "When a car is going by you fast, the plate is easier to read, and easier to memorize," he said.

The plates also offer entertainment on long drives. Potent combinations of car and plate seem endless: MONEY TOX on a lowslung black Datson, MY RV on a Rolls Royce, WNDMEUP on a white Mg, YEAHBUT on a Peugeot with a John Anderson bumper sticker, MYMUDPI on a Brown Honda, GUZZLER on a Buick station wagon, UNMPLYD with a license plate frame that says "I'd Rather be Acting," 1B4Ugo, decadnt, xqqs me x SHIKSA, NO SHIXA,, HUMR ME and DONASK.

Jay Martin, 50, manages the environmental license plate unit of the California Department of Motor Vehicles. "I've gotten a whole new vocabulary since I came to this unit, believe me," she said. She and her staff have a host of foreign-language dictionaries and outside experts to ensure requested plates are not "offensive or misleading." But some slip by.

"We got several complaints about one, KAKIMUN. It means 'Go defecate' in Yiddish," Martin said. "We checked with the anti-Defemation League and they said that was right." The plate owner, "who just wanted to see what happened if he pursued it, I think," gave it up after an administrative hearing agreed that it was offensive.

Martin said PUSSY 1 was allowed because the owner proved that Pussy had been "his nickname used by friends and associates since he was a young boy." The hearing examiners were also influenced, Martin said, by the fact that the man owned two cats.

Martin's staff used mirrors and Pig Latin to decipher some plates. Two objecttionable foreign phrases, one in Polish and one in Spanish, were caught by inmates at Folsom Prison's license plate factory.

The greatest handicap for a motorist seeking an exotic plate, however, is just the sheer popularity of the medium. One motorist who tried to get NI HAO ("How are you" in Chinese) found it was already taken. Gordon, the man accused of robbing the motel who had IM EVIL on his Corvette, said he wanted "unique" plates but that they were only his second choice.

His first choice was IM THE 1. Puzzling Plates Offer Challenge to Travelers

The growing numbers of personalized plates in California and elsewhere provide puzzles for travelers to solve on summer automobile trips. A few samples:

1. IFILRXS

2. IIII

3. Xplosv

4. IM4ERA

5. IMXPNSV

6. imaqt

7. 3TT3V

8. WEXLER8

9. 10SBUM

Answers:

1.) I fill prescriptions. 2.) Four eyes. 3.) Explosive. 4.) I'm for ERA. 5.) I'm expensive. 6.) I'm a cutie. 7.) VETTE when seen in a mirror. 8.) We accelerate. 9.) Tennis bum.