HUNTING for heroin addicts in the stairwell of an unlit, urine-scented housing project, Officers Michael C. O'Hara and Richard L. Whalen pulled out their flashlights and walked upstairs. They checked out the shadows and joked grimly with each other. "How'd you like coming home to this every night?" "Sure smells nice."

Just a routine police chore in the heart of Roxbury. But, as the cops in front of us knew too well, little in the big-city policeman's life is routine.

"You need to sign these releases, in case you get killed--we lost two reporters already," Lt. Robert Faherty had cracked earlier in the evening, and we had sniggered along. Now it didn't seem so funny.

It all started innocently enough. Our escorts were right out of central casting. Boston cops O'Hara, 27, and Whalen, 26: good-humored, clean-cut, baby-faced Irishmen who had grown up in the neighborhood. Once high school rivals, they had become friends in the Academy and had been partners for 18 months.

They were the kind of cops you'd like to think were patrolling your neighborhood.

At Doughboy Donuts, our first stop, we met some of the supporting cast: wisecracking Patrolman James Carnell and his partner. James Browning. Carnell was known as the man whose Dr. Ruth Westheimer impersonations had sent a senior officer to the hospital with chest pains.

They seemed more like a comedy troupe than a police squad. Ten minutes after we'd scarfed down our dinner, however, reality struck...literally. Carnell and his partner had been broadsided in an intesection and rescue workers were cutting them out of their cruiser. They were later treated at a local hospital and released late in the evening, too late to get back on to the five-midnight shift.

Then we were flying at 75 m.p.h., screeching around corners and dodging late rush-hour traffic to get to a reported car theft.

Here we were, two scared, wimpy Harvard students, thrust into the the real world at its worst. Roxbury: the toughest precinct in the state, a place where shootings, stabbings, thievery, fights and druggies are all too commonplace.

"It's the jungle, survival of the fittest," Whalen told us. "They'll kill you. They don't cay-eh," O'Hara added.

Our initial rush proved unnecessary, as the suspicious auto theft proved to be a sidewalk car wash, not a strip--down. In the next hour, though, we found two stripped automobiles and had them towed. Some had been stolen that same day, but we didn't catch anyone.

The highlight of the early evening was driving through dog crap, an event which not only haunted us nasally for some time afterwards, but elicited the first good story.

The evening before, investigating a possible break-in, O'Hara was crawling on a rooftop when he looked down and noticed that he had rolled in something very much like cat shit, making the rest of the night shift seem days long. He was wearing his galoshes now, waiting for his dress shoes to come back from the cleaner's.

"Just my fahkin' luck," he growled, rolling up his window and turning on the air conditioner.

AROUND 7:30 p.m., our mounting blood lust was first satisfied, by word of a two-vehicle collision on Dorchester St. We had been looking forward morbidly to the gory spectacle of a good accident, but when we pulled up and saw the mangled motorcycle lying on the sidewalk, our enthusiasm turned to nausea. It had broadsided a Wagoneer.