The prosecution in the Kate Steinle murder trial may be unable to use the testimony of one of their key witnesses.

John Evans, a former city police inspector, was questioned in court on Monday and testified about the mechanics of a ricocheting bullet.  He further explained that the only way Ms. Steinle could have been killed would have been intentionally:

“A human being held a firearm, pointed it in the direction of Ms. Steinle and pulled the trigger.  This is the only way this could have occurred that is reasonable.”

These statements were critical to the prosecution's case, which argues that the victim couldn't have been shot by a stray bullet.

However, a separate homicide case from 2007 was brought forward by the defense which included accusations that Evans had misrepresented gun evidence.  This ultimately led to an overturned conviction and acquittal.

To make matters worse, Evans was even sued for providing false testimony in that murder case.

Vivian Ho of the SF Chronicle joined the show today to talk about the latest in the Steinle murder trial:

Read Vivan Ho's full article over at SFGate.com, and on Twitter @VivianHo