A teenage boy, numbed by what he described as emotional and physical abuse by his parents, was walking home one winter night from a friend's house when he began fantasizing about a life without them.

Finding a loaded handgun at his house, the 15-year-old "floated" up the stairs and, one by one, pointed the gun at the heads of his mother, father and two younger brothers. Although he does not recall pulling the trigger, he told a forensic psychiatrist that he remembered hearing muffled bangs with each shot.

The chilling account - offered by Nicholas W. Browning to a doctor examining him to determine whether he should be tried for murder in the juvenile system or remain in adult court - cannot be used by prosecutors at trial to convict him of the four killings.

But it will likely play a pivotal role as the teenager's attorneys craft a defense that focuses on his mental state, either in an attempt to prove he might be guilty but not criminally responsible for the deaths or to argue that the shootings did not amount to first-degree murder, defense lawyers and legal experts said.

"Maybe they can mitigate it down to second-degree [murder] or manslaughter," said Brian Murphy, a criminal defense attorney and former Baltimore City prosecutor. "Although it sounds, on its surface, as premeditated as you can get. He walks back, gets the gun, loads it, cocks it, shoots one, walks to next room, shoots another and goes on like that. It's not quite a self-defense argument - because that would be crazy - but maybe it mitigates the premeditation. Kind of like a delayed provocation."

The Dulaney Valley High School sophomore, now 16, lost his bid last week to avoid being tried in adult court, where prosecutors have filed notice of their intention to seek four sentences of life in prison without the possibility of parole. He is accused of fatally shooting his parents, John and Tamara Browning, and his brothers, Gregory, 14, and Benjamin, 11, in the early-morning hours of Feb. 2 as they slept in their Cockeysville home. He had walked the three miles there from a friend's home.

Police said Browning later admitted that he had killed all four members of his family.

That confession will likely be challenged by the defense team at a pretrial motions hearing. Prosecutors cannot use against Browning at trial what he told the psychiatrists who evaluated him for last week's hearing because, according to state law, information gathered to determine whether a case will be heard in juvenile court cannot be used later to convict someone.

Lawyers handling the case cannot comment on it because of a gag order imposed by the judge.

The testimony of psychiatrist Neil H. Blumberg, who was called by the defense, failed to persuade Baltimore County Circuit Judge Thomas J. Bollinger Sr. that the case should be tried in juvenile court. The defendant's mental condition was one of five factors - along with his age, his amenability to treatment, the nature of the crime and public safety - that the judge had to weigh.

But experts said the evidence of Browning's mental state and any mistreatment that he might have suffered at home could play a more important role at trial. Although court-appointed mental health experts attributed the killings to an isolated anti-social act by the teenager rather than a mental condition, Blumberg made a diagnosis of dissociative disorder.

The mental illness is marked by memory loss beyond normal forgetfulness; mental health problems, including depression and anxiety; a sense of detachment; and distorted perceptions.

"Something was radically wrong," Blumberg testified last week. "It is very clear that this was a deeply disturbed young man in a deeply disturbed family in which a gun was available and a tragedy happened."

He told the judge that Browning's parents routinely berated him - and sometimes slapped or backhanded him - over his grades, his appearance, his treatment of his younger brothers, his religious convictions and his morals. The father once grabbed him by his helmet and threw him against a fence after the boy disrespected a referee at a lacrosse game and, on another occasion, kicked him in the stomach at their house after a dispute with one of his brothers, Blumberg testified.

Byron L. Warnken, a University of Baltimore law school professor, said the evidence of emotional and physical abuse, if supported by other witnesses, might not meet the stringent standard that Maryland requires to prove a defendant is guilty but not criminally responsible - the state's equivalent of an insanity defense.

"All of that stuff doesn't sound normal to you and me, but killing four people is not normal either so it's a matter of degree," he said of the symptoms of dissociative disorders. "What it does establish are some facts that might be important one day at sentencing; It's a factor for a kid who is 15 years old at the time of the incident. It's a factor that he was depressed and in la-la land when it was going on. It's a factor if he was, to some extent, a victim. I think that's good stuff for sentencing as to why not to give him life without parole."

Blumberg, who once worked at the state's maximum-security psychiatric hospital, has evaluated about 50 teenagers charged with murder. Although he did not mention it in court, the first case in which he served as an expert witness after leaving the Clifton T. Perkins Hospital was that of a 17-year-old Anne Arundel County boy accused of killing his adoptive parents in 1984.

Larry Swartz of Cape St. Claire ultimately pleaded guilty to second-degree murder charges and was sentenced to 12 years in prison. He was released in 1993.

"It received a lot of publicity because it was one of the first double patricides, certainly in Maryland, and perhaps in all of the United States. It was before the Menendez brothers and all of that," said Ronald A. Baradel, a civil litigator from Annapolis who had handled Swartz's adoption and then helped represent Swartz in the murder case.

The case inspired a book, Sudden Fury, that become a New York Times best-seller and, later, a made-for-TV movie.

The teenager's parents, Kathryn and Robert Swartz, were devout Catholics who were extremely strict with their three adopted children.

Richard M. Karceski, who served as lead counsel on Larry Swartz's defense team, recalled that friends and neighbors of the family witnessed innumerable instances of emotional abuse.

"They had a swimming pool, but the parents would not allow water to splash outside of the pool. The kids would get in trouble if water splashed," he said. "It was strict beyond imagine - and supported by other people."

In addition, medical reports and other evidence revealed the horrible abuse that Larry Swartz suffered before being adopted, starting with his prostitute mother, who abandoned the baby on a doorstep, and later in foster care, Karceski said.

"Our defense was similar to what it looks like Browning's is going to be - the proverbial tea kettle ready to spout its whistle or the proverbial balloon that can only hold so much air before it's ready to burst," he said. "On the night this happened, something snapped in Larry Swartz and he did this to his parents."

The important distinction between the Swartz and Browning cases, though, might hinge on the abuse allegations, Karceski and Baradel agreed.

"Those facts really supported the abuse," Karceski said of his case from 24 years ago. "These facts may, but at this point they don't even seem to be approaching the Larry Swartz set of events."

The Browning case is scheduled to go to trial in December.

jennifer.mcmenamin@ baltsun.com