HOMESTEAD, Pa. (AP) _ A series of rapes of elderly women in this old steel town has forced some women behind locked doors and led at least one to buy a gun, while police are asking most black men in town to be fingerprinted to prove their innocence.

The American Civil Liberties Union has called the fingerprint tactic ''astounding.''

Police Chief Chris Kelly, claiming support from residents, has ordered officers door-to-door in this Pittsburgh suburb of about 5,000 to interview people for clues and ask for fingerprints.

''We just can't sit back now,'' Kelly said. ''How do you tell an 80-year- old victim's family that I was thinking of doing this, but I was worried about the flak I'd get? They don't want to hear about flak.''

Kelly says very few men have refused to be fingerprinted when asked. He said police have accumulated about 115 fingerprint sets so far.

Six women living alone, all between 64 and 85 years of age, have been raped since 1983, including four this year. One 76-year-old woman, the rapist's only black victim, was attacked in her home April 24 and raped in her home Aug. 25, Kelly said.

The women live within a five-minute walk of each other in this town once notorious as the place where seven steelworkers were shot to death during a strike against steel magnate Andrew Carnegie in 1892.

Police are looking for a muscular black man between the ages of 16 and 60. Kelly said police have fingerprints and other evidence tying the attacks to one man.

The rapist has covered his victims' heads with bedsheets so descriptions of him have been sketchy, but the women agree he is black, Kelly said.

''We think he may be somebody respectable, somebody who is very emotionally disturbed but responsible for his actions, somebody who is normal on the outside and able to function within the community,'' Kelly said Monday.

Kelly said the door-to-door canvass has covered about half the town in a little more than a month, he said.

''I know it's never been done before,'' he said. ''It was a very hard decision to make. I've taken an extreme amount of bad publicity for it and pressure, but the people are not complaining. ...

''If you don't live in this community, you don't know what the people are going through.''

A policeman said he knows of one elderly woman who has begun to sleep during the day so she can stay awake and vigilant all night.

''I've bought a gun,'' said one 65-year-old woman who asked not be be identified because of fear of attack. ''I don't know how to use it, but my nephew and his daughter, who's an ex-policewoman, are going to teach me. ... I've also had a phone installed right near my bed this week.''

Locksmith Jack Myers said he has installed about a dozen new locks over the past three months because of the rapist.

''I think I've even done the house of one of the victims. (The rapes) have caused quite a bit of discussion here,'' Myers said.

Despite such precautions, authorities fear many elderly women may not do enough to protect themselves, said Janet Carr, executive director of the senior citizen's center, New Heritage Inc.

''This is basically a family town. This is basically a safe town,'' she said. ''Most elderly women here don't believe rape is something that could happen to them.''

Nathaniel Richardson, 20, who is black, said he has known one of the victims for most of his life and wouldn't mind giving his fingerprints.

''I don't think it's right, but why give police a hassle?'' he said.

The ACLU said the mass fingerprinting violates constitutional rights.

''They've got it a little backward. In this country, you are presumed innocent. You do not have to prove your innocence. The government has to prove you're guilty,'' said Marion Damick, associate director of the Greater Pittsburgh ACLU chapter.

''We are as anxious as anybody that police solve the crime. But we believe they're asking people to give up their valuable right to be left alone. ... It's astounding.'' she said. ''This is a voluntary thing, but there is nothing really voluntary about it. How many people really won't do what the police ask them to do?''