Aide: Gabrielle Giffords to testify at gun hearing

The former Arizona Democrat, who suffered a severe head wound in a 2011 shooting as she met with constituents outside a Tucson supermarket, is not expected to answer questions at the session, according to the aide, who spoke on condition of anonymity because Giffords' appearance had not been announced. Six people were killed and 12 others wounded.

Giffords' husband, retired astronaut Mark Kelly, had already been scheduled to appear before the panel. The two have formed a political action group called Americans for Responsible Solutions, aimed at promoting gun restrictions.

Also testifying will be Wayne LaPierre, executive vice president of the National Rifle Association.