NEW YORK — When police arrested Ronell Wilson, his pockets were stuffed with the type of violent poetry that boys have been scribbling in notebooks since the advent of gangsta rap.

In his lyrics, Wilson called himself "Rated R," warned any challengers to wear a bulletproof vest, and boasted of leaving .45-caliber slugs in the heads of his enemies.

The clumsy verses may never land Wilson a record deal, but to prosecutors, they were solid gold.

Wilson went on trial in federal court in Brooklyn this month on charges he murdered two undercover police officers, and the government presented the lyrics to a jury as evidence that the 23-year-old is a remorseless killer.

Prosecutor Morris J. Fodeman asked jurors to take special note of one stanza: "Ain't goin' stop to I'm dead."

The jury convicted Wilson on Dec. 20, and he now faces a possible death sentence.

The use of rap lyrics at trial is a tactic that has been embraced by prosecutors across the country in recent years.

In cases ranging from small-time robberies to high-profile murders, investigators have discovered that the lead suspects are sometimes wannabe rappers who have written ultra-violent fantasies about murdering and raping their way through life.

Violent lyrics have not been central to the cases, which were built on such evidence as confessions, eyewitness testimony and DNA and other forensic findings. But prosecutors have used rap lyrics to help establish motives and shed light on defendants' characters. Some have brought up the lyrics only during sentencing.

Introducing such writings into evidence is not always easy. But in many instances, there is enough of a resemblance between art and life to persuade a judge to say yes.

The result can be disaster for defendants.

In October, a jury convicted a reputed gang member of murdering a 17-year-old boy in Chico, Calif., after hearing two tracks from a rap CD he had co-written under the street name "Young Saint." The recording warned that rivals would die "looking at my barrel with your very last breath."

In February, an 18-year-old was convicted of a murder near Staunton, Va., after the prosecution brought up a rap he composed in jail that referred to the killing.

Last year, a jury in Alabama sentenced a man named Nathaniel Woods to death for his role in the murder of three Birmingham police officers after prosecutors showed the jury rap lyrics and drawings he kept in jail that glorified the slayings.

"In our case, they gave him the death penalty because he had such a terrible mouth," said Rita Briles, one of Woods' attorneys.

The growing use of lyrics in court has predictably bothered some defense attorneys, who worry about prosecutors introducing violent, curse-filled verses simply to make a defendant look bad in front of a middle-class jury.

"The fallacy of it is that it confuses art with fact," said Bruce Rogow, who defended the Florida rap group 2 Live Crew on obscenity charges in the 1990s. "What you see are prosecutors reaching for anything they can to try to paint bad character."

Philadelphia defense attorney Michael Coard, who also teaches a class on hip hop at Temple University, said attempting to use rap as a window into a defendant's mind is especially problematic, given rap's tradition of overtly ridiculous braggadocio.

"It's about boasting. It's about exaggerating. ... It's about acting," he said. "If Robert De Niro, or Al Pacino or Marlon Brando are charged with shooting somebody, are they going to be playing clips from 'The Godfather' in court?"

Judges occasionally agree.

When rap star Beanie Sigel was sentenced on gun charges in Philadelphia in 2004, a federal prosecutor quoted Sigel lyrics about pouring acid on children and raping pregnant women.

The judge was dismissive, saying that Sigel was simply playing a character for his fans. (Sigel, who has a long rap sheet, was later acquitted of attempted murder in an unrelated case.)

The rapper's attorney, Fortunato Perri Jr., said he has had a tougher time downplaying the significance of rap lyrics written by other, less-famous clients.

"If we have to deal with it at trial, the argument in front of a jury is that it is just kids goofing off, imitating things that they hear from world-renowned artists," Perri said.

In September, a prosecutor in Richmond, Calif., held up cardboard signs bearing rap lyrics as he made his closing argument against a teenager accused of murdering a high school football player. The teen, Darren Pratcher, had written a rap in which he had warned: "If you ain't from our part of town, you're a (expletive) target."

Prosecutor David Brown told jurors Pratcher was simply acting out that philosophy when he gunned down his victim, who was not from the neighborhood.

The jury voted to convict.

"They were words of his soul," Brown said of the teen's writings. "It was my understanding from his lyrics that he knew exactly who he was shooting."

Pratcher, who was 15 at the time of the shooting, could get life in prison.