WASHINGTON - The grieving parents of Trayvon Martin, the 17-year-old black boy gunned down by a neighbourhood watch volunteer who believed he looked suspicious, travelled to the U.S. capital on Tuesday for a congressional forum looking into racial profiling and hate crimes.

Their visit to Capitol Hill comes as the nationwide uproar over their unarmed son's death enters a sadly typical phase in many high-profile, emotionally charged American crime cases: blaming the victim.

"I said before and I'll say it again, Trayvon was our son, but Trayvon is your son," Sybrina Fulton, Martin's mother, told the forum in a packed Capitol Hill meeting room.

"A lot of people can relate to our situation and it breaks their heart, just like it breaks mine."

Her ex-husband, Tracy Martin, thanked people who have helped them "stand tall," adding he's determined his son will not die in vain.

"He's sadly missed and we'll continue to fight for justice for him," he said.

Martin and Fulton believe their boy, wearing a hoodie and walking in a gated Florida community on a rainy February night, aroused his killer's suspicions because of his race.

George Zimmerman, a white Hispanic, says he acted in self-defence after noticing the boy, who was walking back to the home of his father's fiancee after making a visit to a nearby 7-Eleven. Martin was carrying a box of Skittles for his little brother and a can of iced tea.

Zimmerman, 28, claims the teen, who stood six feet, three inches tall and weighed 140 pounds, beat on him prior to the shooting. He had reportedly pursued Martin in his SUV despite a 9-11 dispatcher telling him not to do so.

In recent days, Martin and Fulton have accused the man's lawyers and local police of a smear campaign as investigators face an ever-growing barrage of criticism for failing make an arrest in the Feb. 26 shooting.

"They've killed my son, and now they're trying to kill his reputation," Fulton said this week.

Democrats organized Tuesday's Capitol Hill event. Representatives of various civil rights groups and officials from the U.S. Justice Department, currently probing the case, testified to the forum.

Frederica Wilson, a congresswoman who represents the Florida district where Martin's slaying occurred, said she was "counting down the days" until Zimmerman is arrested for what she described as the "murder" of the teenager.

"I will not rest until an arrest is made," she said. "I will not stop beating this drum until justice is done."

Wilson added she intended to create a national commission to delve into the lives of young black American men, focusing on their health and their interactions with the criminal justice system.

Dennis Parker of the American Civil Liberties Union said Martin's slaying is just the latest example of racially fuelled injustice.

"The killing of Trayvon Martin has once again laid bare the reality that, too often in our nation's history, police actions have been motivated by racial bias and that crimes with an undeniable racial motive have too often been overlooked or swept under the rug," he told the forum.

Martin's slaying has sparked nationwide demonstrations by hoodie-wearing Americans demanding the arrest of Zimmerman. It's also reignited racial tensions in a country where wounds are still fresh following a sorrowed past of slavery and segregation.

U.S. President Barack Obama, the nation's first black commander-in-chief, gingerly weighed in on the case last week, calling on the nation to do some soul-searching while noting that if he had a son, he'd look like Martin.

Those on the right, including Republican presidential hopeful Newt Gingrich and conservative shock jock Rush Limbaugh, have railed against assumptions the slaying was racially fuelled. Gingrich even called Obama's remarks "disgraceful."

Fresh details have begun to emerge about Martin that suggest to some he was a "bad kid" while striking others as utterly irrelevant to his slaying — a standard state of affairs in a country deeply polarized on social and political issues.

The Miami Herald has reported Martin was suspended from school three times in recent months for incidents involving tardiness, writing graffiti on school property and having an empty plastic bag with marijuana residue in his knapsack.

He was serving a school suspension when he was slain in Sanford, Fla., and had never been charged with any crime.

Benjamin Crump, the Martin family attorney, questioned what bearing the details had on the boy's shooting.

"If he and his friends experimented with marijuana, that is completely irrelevant," Crump said. "What does it have to do with killing their son?"

Martin's parents have accused the Sanford police of leaking the information to the media in order to demonize their son. The Sanford Police Department insisted there was no authorized release of the new information, but acknowledged there may have been a leak.

A city official said the leak was under investigation and that anyone found responsible could face dismissal.

Shortly before the event got under way, ABC News reported that one of the lead investigators on the case didn't buy Zimmerman's version of events and wanted to press manslaughter charges on the night of the slaying.

But Chris Serino was overruled when the Florida attorney's office told him there wasn't enough evidence to lead to a conviction, sources told ABC. The man who headed that office, Norman Wolfinger, recently removed himself from the case.

There have been other, more positive details to emerge about Martin: He was a devoted athlete, a loving friend and family member and a good student who did volunteer work for an organization that runs sports and academic programs for youth.

He was gentle and had never been in any physical altercations.

He dreamed of becoming a pilot.

The congressional forum did not solely focus on racial profiling and hate crimes, but also on Florida's so-called Stand Your Ground law, which essentially allows people to use deadly force if they feel threatened. Sanford police have suggested the law was at play in their decision not to lay charges against Zimmerman.

Others have argued that it's Martin, not Zimmerman, who should have been protected by Stand Your Ground if in fact it's true that he attacked his pursuer.