Anne Arundel County police have initiated a crackdown on repeat criminals, especially a small number of teen-age males who a recent study suggests are responsible for nearly half the crimes committed by youths in the county.

The study, conducted last fall by the University of Maryland Institute of Criminal Justice and Criminology, shows about 4 percent of 13,252 male residents born between 1961 and 1964 were responsible for more than 40 percent of the 5,671 major offenses committed by members of the study group by the time they reached age 18.

That same 4 percent were classified by the study as repeat offenders, that is, they committed five or more crimes before reaching age 18.

Anne Arundel County's program follows a similar, widely noted program in the District. The county recently decided to do something about career criminals by creating a special unit of police officers to keep track of them, seek heavy penalties when they are re-arrested and, under one controversial provision, place some under surveillance.

Under the Repeat Offender Program Evaluation--known as ROPE--officials say they hope to catch and punish 50 or more repeat offenders, including juveniles, who commit major crimes each year. The police unit will include six detectives and a supervisor at a cost of about $250,000 a year and will begin next year unless funding can be found earlier.

Both the study and the ROPE program itself emphasize the juvenile offender, with officials noting criminal behavior patterns are usually set before a person reaches age 18.

"We want to get them off the streets through their productive years," said county Police Chief William S. Lindsey, a member of the steering council that commissioned the study. He said the average criminal has a limited span of active years, after which the number of crimes he commits declines.

If repeat offenders can be kept off the streets through their mid-30s, crime in the county could be significantly reduced, said Francis J. Zylwitis, an aide to County Executive O. James Lighthizer.

Under the program in the District, additional charges against repeat offenders may be dropped if the criminal can be returned to jail for a longer time on violation of parole. Also, if a suspect is picked up and found to be wanted on a more serious charge that would bring a longer sentence in another jurisdiction, he may be extradited and the local charges dropped.

The whole point, said Capt. Edward Spurlock, commander of the District program, is to get repeat offenders off the street by whatever means--jail time for parole violation, criminal charges or extradition.

"If we interrupt a criminal pattern of a person who is committing five crimes a week, we've saved five crime victims," Spurlock said.

Since its establishment in April 1982, Spurlock's 62-member unit has made 835 arrests and recovered $3 million in stolen property, including 100 guns and $70,000 in narcotics.

To get the repeat offender off the street, Anne Arundel's seven-member police unit will "enhance and direct investigations of cases involving recidivist offenders and produce high-quality, thorough and evidentiarily sound cases" with the intent of seeing that the criminal is convicted and receives maximum punishment, Zylwitis said. Once convicted, the state parole commission would be notified that the offender is a recidivist, a point officials hope will be taken into consideration when he comes up for parole.

Under state law, anyone convicted twice of major crimes, such as rape and murder, is subject to a mandatory 25-year prison term without parole. Three major-offense convictions result in a life sentence without parole.

Ann Arundel State's Attorney Warren B. Duckett, who for five years has operated a career criminals program that singles out repeat offenders for more vigorous prosecution without plea-bargaining, said he is enthusiastic about the new role of police, courts and the parole commission in targeting repeaters.

He said he is not enthusiastic, however, about the provision permitting police to put career criminals under surveillance without any indication they are involved in current criminal activity.

"That has a chilling effect on me," Duckett said. "Just to follow a person for the sake of following him, that troubles me." The police could be better used, he said. "I just don't know if we have to be doing that."

John Roemer, executive director of the Maryland branch of the American Civil Liberties Union, said police "have the right to make investigations and watch people they have good reason to believe are involved in criminal activity."

But it is "extremely difficult" to predict the behavior of recidivists, he said, and the presence of police officers around a released convict could hamper his attempts to enter mainstream society.

Zylwitis said surveillance has been upheld in recent court cases and will be conducted in close consultation with Duckett's office.

The only other metropolitan jurisdiction focusing on repeat offenders is Prince George's County, which does not have an established program but does have a handful of officers working with the District.

Lt. Robert E. Nelson, who oversees the investigative unit, said it has recovered $100,000 to $140,000 in stolen property in the last nine months.