Some people are fooled by her appearance - her blue eyes shadow, her pierced ears - but her male co-workers call her Mad Dog.

That's after she pins up her waist-length brown hair, plants a District police officer's cap on top of it and straps on her .38 caliber service revolver.

Officer Maralyn Hershey, 28, has never spent much time contemplating changes in modern sex roles while prowling dark alleys and back streets, confronting suspected thieves, addicts, pimps, hookers, drunk-and disorderlies, and other denizens of the midnight hours in Washington's highcrime 14th Street NW territory.

"She's only got one flaw." grinned Officer Lawrence P. Green, a some time partner of Hershey. "She's too aggressive."

None of this has changed, apparently, since Hershey got a partner named Dorothy.

Without fanfare, the D.C. Police Department recently made Hershey and rookie Officer Dorothy Cobey the first all-female scout car team on the streets of Washington and, as far as they know, and city in the country.

This was the latest in a series of steps through which the department has, since the early '70s, increasingly blurred the lines between male and female police duties and become a model for other cities where resistance to the idea of uniformed females remains.

There are 308 policewomen on the 4,500-member force here, including 13 investigators, six sergeants and one lieutenant: 244 women (or 79 per cent) are in some type of street unit.

"I guess some women would view this as the ultimate for women's lib." Hershey said the other night as Scout Car 101 drifted through the ice-encrusted streets, "but really, we're just two police officers . . . I'm not a libber, are you. Sis?"

Her cool-eyed partner shrugged, smiled and continued scanning the streets.

It was 3 a.m. The officers could figure that the night and the subfreezing wind had effectively driven most innocents from the streets. Along certain blocks of 14th Street, the men and women who huddled in clusters on corners, their breath blossoming white, or sat in parked Cadillacs with the engines purring were not, as the policce put it in their street slang parody, "waitin' for no bus."

This night, like other nights. Scout 101's route took it between this bleak region and the stylish hotels and shops of Conneticut Avenue a few blocks to the west, with side trips orchestrated by commands that came in short bursts from the police radio.

Hershey and Cobey work out of the third district station (They call it Three-D) at 1620 V St. NW. That night, they were on the shift that ran from 10:30 p.m. roll call to 7 a.m. They are partners for three shifts a week and as part of routine shift rotation, draw male partners for the other two.

According to their supervisor, Sgt. Vernon Gehris, "these two do more work than most of the men. Uh, change that to 'other officers.'"

"Don't tell Maralyn we call her Mad Dog," requested another coworker.

Hershey is dramatic, full of nervous energy, tall (5 feet 8) talkative, a heavy smoker, white, and single. Cobey is more reserved, throwing out opinions and witticisms sparingly.

She is smaller physically, black, and a non-smoker. She is married and has a 4-year-old daughter. The two feel they make a well-balanced partnership.

The popular crimes on their route this particular week were auto larcenies and "hooker robberies" (in which prostitutes rolled their customers) and the usual run of "disorderlies" each different from the other, and potentially dangerous.

"just two police officers," as Hershey puts it, they checked clanging burglar alarms, warned a few potential prostitute robbery victims, approached autos in which they spotted familiar faces to run name checks and auto tag numbers for possible warrants, and provided back-up to other scout cars doing the same thing, just as others provided back-up to them.

On the street that night, on man called them "honey," and there were a few double-takes, but generally, they got the same indifference or obscentity-laced chatter as their male counterparts.

At 3:30 a.m., Hershey and Cobey were running into the front yard of what they described as a "trick pad" at 13th and Corcoran streets to help nab an alleged mugger who turned out to be unarmed. A heroin addict, they said. The complaint had come from one of three 16-year-old youths from Rockville - bright, middle-class, two white, one black - who had come to the District for excitement and, after some drinking, ended up at this house.

Because one of the youths had no money to pay a prostitute, he had stayed in the back of his friend's car to sleep. That's when the man tried to rob him, he said. He asked, sheepishly, that the police not "bother" his parents.

Back at Three-D, when she was reading the suspect his rights, Hershey took some teasing from male officers because the suspect's pants were unzipped and he asked her to zip them up. She declined.

Hershey figures, however, that there is nothing really important in the line of duty that she can't handle as well as a male officer.

During her almost seven years on the force, Hershey has collected plenty of "war stories." She has been fired on once, and was on the scene in three other incidents where gunfire was exchanged. She has engaged in high-speed pursuit and once broke her right hand trying to collar a suspected auto thief.

She has received two cash incentive awards from the department for "outstanding performance of duty," and numerous letters of commendation, she said, "and I have also had my share of disciplinary matter," including one fine for misconduct (drinking on duty). "That was during my John Wayne days, when I was being 'one of the guys,'" she said.

Hershey attracted attention - and some resentment - early in her career when she got a D.C. police sergeant fined and stripped of his rank for soliciting her while she was posing as a prostitute during a vice crackdown.

Hershey is also reported to be the police woman who detained a U.S. congressman on charges of soliciting sex about a year ago, though she doesn't discuss it. The congressman was not charged because of the department's policy of congressional immunity, but the incident led to an order by the department ending that policy.

The daughter of a former FBI agent, Hershey attented Prince George's Community College for a year before tyring police work - on an impulse, she said.

"When I was a little girl, I didn't play cops and robbers and I wasn't the bully of the neighborhood or anything," she said.

When she entered the force, policewomen were not uniformed and were generally relegated to social worker jobs involving juvenile or family problems and certain types of vice work.

In 1972, Hershey was one of 80 policewomen the department ordered into uniform. The following year, it became the first major department to assign women the same duties as men.

"It was quite a transition," Hershey said. "God, I thought, we'll be out there sort of exposed, in a totally masculine job, wearing a gun . . . Yuk! It took me a good two weeks to get into the swing of things, to get used to the response from the community. The 'eyeballs,' you know, the stares."

The role of women expanded, meanwhile, on both sides of law enforcement. In September, 1974, Officer Gail A. Cobb became the first policewoman in the nation to be killed in the line of duty. Hershey notes that more women also appear to be commiting serious street crimes.

Hershey feels the danger involved in her work is unrelated to gender. "Nobody wants to get hurt, but there's about 2 per cent of the people you run into that doesn't want to go to jail, I mean physically doesn't want to go, you know," she says ". . . We know that if somebody doesn't want to go, sex, color, or anything else doesn't make any difference if they're going to try kill you."

Like other police officers, Hershey used words like "experience" and "instinct" to describe the ingredients necessary to survive and to avoid getting you partner hurt.

Between calls, she and Cobey chatted about the advantages of being able to talk to their scout car partner about their gynecological problems.

Cobey teased Hershey about not always being so tough. "When they tell you to check out an 'unusual or suspicious odor,' you know what that it. It's It's a dead body," Cobey said. "We call them 'stinkers.' We had one on New Year's Day, and Maralyn threw up."

"I've handled plenty of fresh ones. Homicide vitims. I'm not squeamish about the sight of blood," Hershey said. "Burt this was New Year's Day, and I had a hangover, you know? Oh, go ahead, make your partner look like a sissy."

When someone teasingly compared her to one of "Charlie's Angels" (a hit TV series). Hershey turned thumbs down, "Barney Miller" is her favorite cop show, she said.

Hershey says female officers are "pretty well accepted now." both in the community and among other officers. "Sometimes winos and so forth, they'll put their hands up ans say, 'Ooooh, lock us up!' or 'Gee, how'd you like to go to jail with that!' Dot and I just smirk to ourselves and give the old professional 'Good morning, sir . . . '"

As for male officers, she said, "most of their criticisms are of specific female officers, just as they criticize other male officers."

Cobey, who joined the force a year and a half ago, said, "I like what I'm doing. I woundn't give this up for a desk job. Here, you never know what you'll be doing from one day to the next."

She doesn't take her work home with her, she said, even though her husband is himself a military man.

"When I go home, I leave my job outside. If I was in danger, or no natter what happened, I don't talk about it, and he doesn't mention it."

As for "Mad Dog" Hershey, she is determined to "make rank." She took the sergeant's examination early last year, but her score and her precinct rating were not high enough, she said. "I've got a lot more studying to do. I'll be 29 when I'm eligible for the test again, and feel I will have grown up quite a bit."

She's vaguely dissatisfied with the social life her work allows her. Because of shared interests anderratic police schedules, it centers largely around the same people she works with.

"I'd like to get some day," she said. "But when I'm not working, it seems like I'm in court. And when I'm not in court, it seems like I'm sleeping. I just wonder if it will ever happen to me."