"To have them in the gallery during the speech is a strong reminder to Congress that the American people want action on these issues," said Langevin, who has used a wheelchair since being paralyzed in a shooting accident as a teen.
Langevin was a 16-year-old Boy Scout cadet working with police in Warwick, R.I. He was in a locker room watching officers examine a gun they thought was unloaded, when the weapon accidentally fired. A bullet ricocheted off a metal locker and severed Langevin's spinal cord.
Taking sides on the gun issue while coping with grief can be a stunning and disillusioning experience, say veterans of victim advocacy.
"Families are not prepared to go through the onslaught," said John Walsh, host and executive producer of TV's "America's Most Wanted" show, who began his crime-busting crusade after the abduction and murder of his 6-year-old son, Adam, in 1981. Victims' relatives, he said, can get frustrated when their activism doesn't translate into swift action.
"They're not prepared for all the shenanigans in Congress," said Walsh. But, he added, some good could come from Sandy Hook. "There is a tiny window here before everybody forgets about it. This could be a great time for these parents to make a loud statement."
In his speech, Obama is expected to urge support for his plan to ban assault weapons and require background checks for all gun buyers. Last month he released his package of proposals for curbing gun violence in response to the Newtown shootings and vowed to use the powers of his office to fight for the proposals.
Most of them face tough opposition from the NRA and its friends in Congress. Conservative accused Obama of using children as political props. When he announced his gun proposals at the White House, he was surrounded by some kids who had written him in support of further gun restrictions.
While no family wants to be exploited, many in Newtown want to have a role in seeing something come of the tragedy, said Rep. Rosa DeLauro, D-Conn.
Their testimony, she said, "puts a tangible human face on the issue."
Jim Tyrell, a Warwick, R.I., bartender whose older sister, Debbie, was shot and killed nine years ago during a robbery at the convenience store she owned, said he's attending Obama's speech as Langevin's guest.
"Somebody took her life with a gun, and here I am trying to save another person's life by getting guns off the streets," he said.
Tyrell said he's not daunted by the prospect of public criticism. "If somebody criticizes me, that is their opinion. I am not looking to offend anybody else, I just want to tell them my story and what happened to our family."
Melia reported from Hartford, Conn. Associated Press writers Pat Eaton-Robb in Hartford and Darlene Superville in Washington contributed to this report.
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