THE envelope carrying the letter Katharine Czajka sent to her parents from the York Correctional Institution in Niantic was decorated with childish doodles and song lyrics, and was sealed "with a kiss." The markings would not have been out of place in the margins of a bored high school student's social studies notebook. But to Katharine's mother, Joanne Davidson of New Milford, they felt grossly out of place stamped with a return address from an adult prison.

"This is what she sends me on every envelope," Ms. Davidson said in a recent interview at a diner near her Danbury office. "She's a kid."

To Ms. Davidson, Katharine, who is 17, may be a child, but to [1] Connecticut's Department of Correction she is an adult who faces adult charges of burglary, larceny and stealing her mother's car. Connecticut is one of three states where people as young as 16 are automatically charged as adults. The others are New York and North Carolina. In most states, those under 18 are sent to juvenile detention and receive services targeted to juveniles. In some states, the cutoff age is 17.

A bill being considered in the General Assembly seeks to change the law so that 16- and 17-year-olds are treated as juveniles as long as their crimes are not so serious as to merit stricter punishment. It passed through the Judiciary Committee on a 28 to 12 vote on Monday and was sent to the Appropriations Committee for another vote.

"We need to change the way we address services for youth," said State Representative Toni E. Walker, a Democrat from New Haven, who pushed the bill through the Judiciary Committee. "The State of Connecticut, if we don't watch out, will be parents to a lot of kids through the correctional system."

But the bill has encountered opposition in the criminal justice system, with Chief State's Attorney Christopher L. Morano calling it "disastrous for the people, for the public safety of the state, for the juveniles that would be part of the court, and for the system in general" in testimony before the Judiciary Committee last month.

Cost is also a concern for some of the bill's opponents. A report for the Legislature, released by a state panel in February 2004, found that raising the age of adult jurisdiction would cost nearly $84 million in operating expenses and $81 million in construction expenses. The Judicial Branch is currently updating those estimates.

The law's proponents argue that continuing to house 16- and 17-year-olds in adult prisons will cost the state more in the long run and turn troubled teenagers into hardened criminals. Some community activists hope changing the law can spur the state to reform the entire juvenile justice system, making it more community-based and emphasizing prevention over punishment.

Raising the age would certainly force a drastic shift in the way the state provides services to 16- and 17-year-olds accused or convicted of crimes. In the 2004-5 fiscal year, 15,600 children through the age of 15 went through the juvenile court system, while 13,218 16- and 17- year-olds were sent to adult criminal court. Adding thousands of people to the juvenile court system would mean a huge shift in state resources, state officials said.

Proponents of the bill contend that the current system does not serve young people well. Those who are 16 or 17 are sent to prisons instead of juvenile detention centers, even while awaiting trial. Boys are sent to the John R. Manson Youth Institution in Cheshire, which houses 14- to 20-year-old inmates. As of March 1, there were 670 inmates at Manson.

Manson was in the news last year after David Burgos, 17, who was being held on a probation violation, hanged himself with a sheet there in July. His mother, Diana Gonzalez of Bristol, said that she had trouble getting any information about her son while he was locked up — she did not visit him during the four months he was at Manson — and that he was not getting the services he needed for his bipolar disorder, attention deficit hyperactivity disorder and depression. Ms. Gonzalez testified in favor of raising the age before the Judiciary Committee last month.

"You take a kid with these problems and lock him up and see what it's going to do to him," she said in a recent interview.

As with every prison suicide, the Department of Correction is investigating Mr. Burgos's death, and a spokeswoman would not comment on specifics of his case.

The Niantic prison is the state's only women's prison, and young offenders like Katharine Czajka are held in a separate area from adults. Niantic had 1,290 inmates as of March 1, and 27 of them were 18 or younger. Ms. Davidson, Katharine's mother, said she was concerned that her daughter was interacting with older inmates at meals, in vans on the way to court, and when she went to get medicine. She also complained that her daughter was not placed in prison