WASHINGTON: A woman whose Chicago police officer brother was fatally shot in 2010 says it's time for Congress to pass laws keeping guns from criminals. Another woman says firearms restrictions prevented her from protecting her parents when they were killed in a 1991 mass shooting in a Texas restaurant.

The two were among several witnesses taking opposing sides Tuesday as the Senate holds its second hearing on gun curbs since December's shooting deaths of 20 children at an elementary school in Newtown, Connecticut. This time, a Senate Judiciary subcommittee is examining the constitutionality and effectiveness of federal firearms limits.

"We need to keep guns out of the hands of criminals and those who are mentally unstable," the subcommittee's chairman, Democratic Sen. Richard Durbin of Illinois, said in a brief interview Monday. "I hope everyone will acknowledge that within our Constitution is not only an individual right to bear arms, but the collective right of Americans to be safe."

A Republican on the panel, Sen. John Cornyn of Texas, said existing gun laws are not being effectively enforced. He cited the often ignored requirement that states make mental health records available to the federal background check system.

"I'm still interested in somebody identifying which of these laws would have prevented any of these horrific incidents," Cornyn said Monday. "I'm not interested in just doing something that's symbolism."

President Barack Obama wants Congress to enact new curbs, including bans on assault weapons and large-capacity ammunition magazines and a requirement that all gun buyers be subject to background checks, not just sales by federally licensed dealers. Obama is expected to push anew for his plans in his State of the Union address Tuesday night.

Most Democrats have been more receptive to Obama's proposals than Republicans, most of whom - along with the National Rifle Association, the influential gun rights lobbying group - have opposed the president's plan.

The universal background check has the broadest support and is expected to be a centerpiece of legislation Senate Judiciary Committee Chairman Patrick Leahy hopes to write in the next few weeks. The assault weapons ban is given little chance of enactment, and passage of a ban on large-capacity magazines also seems doubtful.

Other witnesses testifying Tuesday included Timothy J. Heaphy, the Obama-appointed U.S. attorney for the western district of Virginia, and two legal experts.

In prepared testimony, Suzanna Gratia Hupp described being in Luby's restaurant in Killeen, Texas, when a gunman crashed his truck through the front window, emerged and fatally shot 23 people, including her parents, and wounded many others. Hupp says she had left her gun in her car because Texas law barred her from bringing it into the restaurant.

"I can't begin to get across to you how incredibly frustrating it is to sit there, like a fish in a barrel, and wait for it to be your turn, with no hope of defending yourself," said Hupp, now a Republican Texas state official and gun rights advocate.

She added, "The only thing the gun laws did that day was prevent good people from protecting themselves."

Taking a different view was Sandra J. Wortham, whose brother, Thomas E. Wortham IV, was shot dead outside their parents' home by robbers, though he and his father, a retired police sergeant, fired back.

"The fact that my brother and father were armed that night did not prevent my brother from being killed," Wortham said in prepared testimony. "We need to do more to keep guns out of the wrong hands in the first place. I don't think that makes us anti-gun. I think it makes us pro-decent, law-abiding people."

Laurence H. Tribe, the liberal Harvard Law School professor, said in his prepared testimony that nothing Obama has proposed "even comes close to violating the Second Amendment" of the U.S. Constitution which guarantees the right to bear arms.

Tribe said more sweeping proposals to take guns away from citizens "have been decisively taken off the table" by Supreme Court rulings in 2008 and 2010 that overturned handgun bans by the District of Columbia and other state and local governments.

Differing from Tribe was attorney Charles J. Cooper, who has long defended gun rights and represented the NRA.

Cooper said those same Supreme Court rulings "establish that the Second Amendment guarantees a fundamental, individual right to keep and bear arms." He said Obama's proposed assault weapon and high-capacity magazine bans were unconstitutional because gun rights "cannot be circumscribed by appeal to countervailing government interests."

Highlighting the political appeal of the gun fight, numerous Democrats were inviting people affected by gun violence to sit in the visitors' galleries during Obama's nationally televised speech. One Republican lawmaker invited Ted Nugent, the aging rock-and-roller and vocal gun-rights supporter.

Former Rep. Gabrielle Giffords, the Arizona Democrat shot in the head two years ago in Tucson, and her husband, former astronaut Mark Kelly, will attend Obama's address. Earlier in the evening, the two scheduled a fundraising event for their new political action committee, Americans for Responsible Solutions, which favors firearms curbs.