"I have learned to never second guess a jury. You never know what a jury is going to decide because you are not in the courtroom," Retired Supreme Court Justice Penny Wolfgang said.
While we may never know why the jury made this decision, legal experts weighed in on why they think Casado was acquitted.
"Having been a prosecutor for ten years and doing homicide trials and trials that involved manslaughter, the problem in trials like this is you have to prove that he intended to shoot and kill the victim or shoot and seriously injure her," Harmony Healy, a prosecutor turned defense attorney at HoganWillig Attorneys at Law, said.
Casado was acquitted on charges of second-degree murder and first degree manslaughter. Both of those charges require the prosecution prove Casado intended to kill or hurt Wierzbicki beyond a reasonable doubt.
"I think the turning point is whether he knew and understood that he could injure her with the gun he was using and that he intended to do that," Healy said, "I think that some of the key things here were the 911 call. It's my understanding that on the 911 call he said he didn't mean to shoot her. He didn't know that the rifle he shot would injure her. That's my understanding from his interview as well."
But retired Wolfgang said the case likely rested on the justified homicide defense.
"In my experience with what the law says, I'm assuming that the jury believed the justification defense since the only issue was self defense or whether he was justified," Wolfgang said.
Wolfgang said to prove justified homicide, or self-defense, there had to be proof Casado feared for his life.
"There had to be evidence showing that he, and I assume there was, that she had threatened him. That he feared for his life. That this was a reaction that was quote unquote justified by the circumstances," Wolfgang said.
Regardless of why the jury acquitted Casado, he cannot face charges for this crime in criminal court again. The prosecution cannot appeal the verdict.
"The law says there can not be a new trial because it would be double jeopardy. Criminally he can not be held responsible," Wolfgang said.