SHORTLY before midnight, Richard Gruber, looking drunk, slouched against a dirty wall leading into the subway, a gold chain and fancy watch flashing from his body.
A couple of men exiting a train noticed Mr. Gruber and saw an easy opportunity for self-enrichment. One drew a gun and pointed it at Gruber, whose eyes were closed.
What the criminals did not know is that Gruber is a police decoy, expert at feigning intoxication. Seconds later, after the thieves had taken his valuables and put away their gun, a team of backup police officers emerged from several hiding points and arrested the robbers.
Long portrayed as an evil underworld filled with shadowy dangers, New York City's subways have become much safer over the past five years.
Crime has fallen by nearly half, from 18,300 subway crimes in 1990 to 9,200 last year. Stepped-up police efforts, including the special decoy unit, help account for the decline, experts say.
Others have expressed strong concern that police decoy operations are often unneeded and unjust, resulting in the arrest of people who might not otherwise commit crime.
``The decoy operations produce zealous officers who, in their desire to demonstrate the need for this type of activity sometimes engage in entrapment techniques,'' says Norman Siegel, executive director of the New York Civil Liberties Union.
Gruber's gun episode was unusual in that subway thieves preying on decoys rarely use weapons. ``It's everybody's worst nightmare for something like that to happen,'' he says. But ``it's part of your job.''
ON a recent night, police officer Alton Bush gives his premiere performance off and under Broadway as a decoy at Times Square. He wears a gold-plated marijuana leaf on a chain around his neck, a fake Gucci watch, a gold bracelet, and a gold ring loosely placed on his finger for easy removal. For added effect, he rubs some alcohol on his face, but does not allow it to touch his lips: Police are forbidden to drink on the job, even when posing as drunks.
Bush stumbles down a ramp inside the subway and leans against a banister as though unable to move a step further. As he gets into the role, he begins to drool.
The performance works in New York City because most of the 1 billion passengers who rode the subway system last year long ago became accustomed to walking past the homeless and other distressed people without taking much note.
As Bush waits, Louise Dantzler, known as the ``eyes'' of the operation, peers from the peephole of a subway service office about 20 feet away. Speaking in a muted voice, the policewoman describes by radio a suspicious person approaching the `D' [decoy].
``He's talking to the `D,' '' Ms. Dantzler says. ``He's waiting for the passageway to clear out.''
The man, like many thieves, is testing out the decoy by touching him, talking, and sometimes taunting him for 15 minutes.
Then suddenly Dantzler broadcasts: ``I think he's going for the bracelet.''
Dantzler's audience, eight undercover police officers posted near subway exits, perk up, ready to rush out and apprehend the man once the ``eyes'' gives the word. ``When things get into play your heart is thumping and your adrenaline is rushing,'' says officer Derek Quick.
Then, as the tension builds, the man suddenly loses his nerve and leaves without taking anything. On this occasion, as on many nights, the trap fails.
New York is believed to have the only full-time decoy unit in the country. In 1994, two decoy teams made 155 arrests, a number police say hides the unit's real value.
``The decoy operation's success is not judged on how many arrests they make, but on whom they are arresting,'' says Transit Police spokesman Albert O'Leary.
``What we see as a success is when we get somebody who is a career criminal who literally supports themselves by stealing property from passengers on the subway,'' he adds.
Another goal is to raise doubts in a would-be criminal's mind that a helpless drunk could in fact be an undercover officer.
One drawback of undercover and decoy operations - an area using 10 to 15 percent of the city's 4,300 transit police - is that it offers less visible assurance to the public. So even as police boast about the sharply lower crime rate in the subways, many New Yorkers still have doubts about safety.
SINGLE incidents can go a long way to undermine public confidence. For example, an undercover stake-out of suspected pickpockets in midtown Manhattan beneath Rockefeller Center turned into pandemonium earlier this month when police started chasing the suspects with guns drawn. One police officer accidently shot himself before two suspects were arrested.
``The perception of crime on the subways has always been at odds with the reality,'' says Clifton Hood, author of ``722 Miles: The Building of the Subways and How They Transformed New York.'' ``One reason for that is that subways are an enclosed space that give rise to feelings of claustrophobia.''
Even if their work often goes unnoticed, decoys do undertake a very physically demanding task.
After about two hours of making an unsightly spectacle of himself, decoy Bush needs a break, and the team assembles in a van on the street above. The other officers congratulate him on his convincing first outing as a pseudo drunk.
Tonight the effort failed. But as in a house with many mice, police say the trap is likely to snare a thief next time.