HOUSTON — The family of a man who was fatally shot by an undercover suburban Dallas police officer during a drug bust has filed a lawsuit alleging that a badly designed flashlight mounted on the officer's handgun led to the death.

Michael Anthony Alcala, 25, was shot and killed on Oct. 13, 2010, during an alleged attempt to sell heroin to an undercover Plano police officer in a parking lot. The officer, a sergeant, told investigators he was trying to turn on the flashlight when he accidentally fired his weapon, killing Alcala while trying to arrest him, according to an affidavit taken as part of a police inquiry into the shooting.

"I was attempting to squeeze the light mechanism when my weapon fired and the suspect fell to the ground. ... I never intended to fire my weapon. I never intended to have my finger on the trigger," the officer, whose name was not made public, said in the affidavit.

No criminal charges were filed in the shooting. A lawsuit Alcala's family filed against the city of Plano was settled last year for $245,000.

The family's lawsuit against SureFire Holdings LLC and SureFire LLC accuses the California-based companies of defectively and negligently designing the flashlight. The lawsuit, announced Monday, was filed in state court in Orange County, Calif., last week. It asks for unspecified damages.

SureFire spokesman Ron Canfield said the company had no comment on the lawsuit. SureFire calls itself the leading manufacturer of high-performance flashlights and weapon-mounted lights.

The lawsuit says the SureFire X300 gun-mounted flashlight has a grip switch that allows the user to turn it on by squeezing a bar under the trigger guard. Alcala's family alleges that the location of the grip switch under the trigger "creates a substantial risk that the user will accidentally pull the trigger and fire the gun while intending only to activate the flashlight."

Canfield said in a statement that SureFire introduced the first light designed to be mounted on handguns in 1986 and introduced its X-series WeaponsLights — intended primarily for attachment to handguns — in 2004.

"There are well over 100,000 SureFire X-Series lights and tens of thousands of optional grip-activated 'DG' and 'SL' switches in use today, and our competitors have sold thousands of other pistol-mountable lights themselves," Canfield said in the statement. "During this 25-year period this was the first reported safety-related incident involving our pistol-mounted lights and switches. These figures alone show that SureFire WeaponLights, and weapon-mounted lights are safe."

Les Weisbrod, a Dallas-based attorney for Alcala's family, said he believes the gun flashlight remains unsafe.

"More deaths will occur if something isn't done," he said.