San Francisco police criminalist and firearms expert Gerald Andrew Smith testified in the Kate Steinle murder trial on Tuesday about the alleged murder weapon's potential for accidental discharge. Smith described the pistol, a Sig Sauer P239, as having an "internal, passive safety," according to KQED's report of the trial. This means that the pistol is prevented from firing unless someone directly pulls the trigger. Such mechanisms are designed to prevent misfires from, say, dropping the pistol. Smith said, "If this gun was dropped, the only way for it to discharge is if something pulled the trigger during the dropping of the gun."

The defense's argument rests solely on the belief that the accused, Jose Ines Garcia Zarate, did not intend to pull the trigger, and that it went off as he was unwrapping it from a bundle of clothing after finding it underneath a chair on Pier 14. Matt Gonzalez, Garcia Zarate's attorney, described what could possibly have happened to trigger that, saying, "If this gun were wrapped in something, most likely Mr. Garcia Zarate’s hands and fingers would have been probing the object as he handled it. That’s when he could have hit the side of a trigger and depressed it back."

Smith's testimony included testing the pistol to find out how much force it would take to pull the trigger back and fire. The P239 has two "modes," single-action and double-action, each of which requires different amounts of force in order to get the gun to fire. Single-action mode means that the gun's hammer is cocked, or already pulled back and ready to fire, whereas double-action mode means the trigger does the pulling and releasing in one squeeze. CBS' report says that Smith found the single-action mode required the application of 4.8 to 5.5 pounds of force, and the double-action mode required 9 to 9.8 pounds of force. Neither of these were out of the norm for the pistol, which Smith also said was in good condition prior to being thrown into the Bay.

According to ABC 7, Gonzalez told reporters: "I have handled this very firearm, this trigger pull is extremely light, that's why I am so confident that I would like the jury to be able to handle it. And anybody who believes that the gun cannot fire accidentally, I have no doubt that would settle it." Gonzalez has already asked Judge Samuel Feng to allow the jurors to dry fire the gun to see what that kind of force feels like in their hands, says the Examiner. "We want the judge to allow the jury to dry fire it in single-action mode. I am very confident that if you handle this firearm in single-action mode and depress the trigger, it’s very light." Judge Feng has yet to decide on whether he wants to allow that or not.

This all follows Monday's testimony from John Evans, another firearms expert and retired police investigator, who said that according to his vector analysis, he could trace a path from where Garcia Zarate was standing to the ricochet mark found on Pier 14 to where Steinle fell after being shot. Gonzalez argued that this analysis used insufficient data, as only one of the points was a "fixed point," and determining a proper bullet trajectory requires at least two fixed points. Still, Evans said that he believes Garcia Zarate pointed the gun at Steinle and fired.

All previous coverage of the Kate Steinle shooting on SFist.