Key evidence in the Kate Steinle murder trial was presented on Monday, as a firearms specialist and retired police investigator testified about the alleged ricocheting bullet that killed Steinle in 2015.

Per the Examiner's report on the day's proceedings, John Evans, the testifying specialist, said that the bullet traveled from the gun to Steinle's back after it impacted on the ground not far from where the accused, Jose Inez Garcia Zarate, was sitting. The defense, Matt Gonzalez, had been maintaining that Steinle's death was the result of a "freakish ricochet," and that the gun fired "accidentally" after Garcia Zarate picked it up and unwrapped it. This is where the heart of the case seems to lie, as the prosecution's argument says that Garcia Zarate aimed the gun at Steinle (or a crowd of people near her) and fired. In his testimony, Evans said, "A human being held the firearm, pointed it in the direction of Ms. Steinle and pulled the trigger, firing the weapon and killing the victim. That is the only way that this could have occurred that is reasonable."

Evans also brought up a common tendency amongst shooters where they pull the trigger too hard. He said, as the Ex reports, "When individuals are pressed for time, also when they are not particularly well-trained, they have the tendency to jerk the trigger, which causes the gun to point lower, causing exactly this kind of shot, known as a ‘skip shot.'"

Gonzalez questioned Evans' findings, saying that in order to determine the path of a bullet, one needs to know about at least two fixed points. Evans had apparently conducted a "vector analysis" to determine the possibility of a ricocheting "skip shot." That particular form of analysis uses only one fixed point, which, in this case, was the point at which the ricocheting bullet bounced off the pier and allegedly towards Steinle. KQED described Evans' process, saying that he pointed a laser from one of the swivel seats where Garcia Zarate was sitting, tracing a direct path from that seat to the ricochet point. Then, from there, he traced another direct line to the area where Steinle was standing. Both Garcia Zarate's seat and Steinle's positions were approximate, allegedly leaving the ricochet point as the only "fixed point."

The AP reports that Evans said guns "do not fire by themselves," and that discharges — accidental, negligent, or otherwise — require someone pulling the trigger. Per the AP, "Evans said he believed Garcia Zarate pointed the gun at Steinle and pulled the trigger." The Examiner has the exact quote from Evans, who said, "I’m not saying it’s impossible, I’m saying in the vast majority of cases, the way to make a weapon fire is to hold it and pull the trigger." Gonzalez pointed out that the SFPD had 29 accidental discharges between 2005 and 2011. When pressed about Garcia Zarate's alleged intent, Evans said later, "I cannot say that it was an accident or not."

The trial continues to occupy much of the country's attention, as it was — and still is — being politicized as an example of the dangers of becoming a sanctuary city, despite the protests of Jim Steinle, Kate Steinle's father. Garcia Zarate was wanted by federal immigration agents, who asked that the SFPD hold him for an extended time while they began deportation proceedings. Garcia Zarate had been deported five times before this incident, and that would have been his sixth. Steinle's murder was a big talking point during Trump's presidential campaign, as Garcia Zarate's status as a Mexican national and undocumented immigrant ignited anti-immigration fervor.

Previously: 'I Thought It Would Be Pretty Safe,' Says Federal Ranger Whose Gun Was Stolen And Used In Steinle Killing