BOISE - Doctors say proving someone is mentally incompetent is a complicated process .

"It's a complex look at past, present and the risk for future dangerous behavior," said Charles Novak, a local psychiatrist.

Over the past year there have been many sensational murder cases.

John Delling is charged with killing two men.

Todd Hagnas pleaded guilty to killing his two roommates and burying them in his bench home before setting it on fire and who can forget 17 year old Ethan Windom, who brutally beat and stabbed his mother to death.

So, why did Delling's mental evaluation diagnose him as not competent to stand trial while Hagnas and Windom were found competent?

"The main element is that at some level the people understand and truly do know the difference between what's right and what's wrong," Novak said.

Here are the facts you need to know first, a defendant is evaluated
if a doctor finds them incapable of assisting in their defense and they have no understanding of the charges they're facing, then they're found incompetent to stand trial.

"There's no simple way to figure it out," Novak said.

In Delling's case he was diagnosed with severe paranoid schizophrenia and was not able to assist his defense.

Doctor's say Todd Hagnas suffers from light dementia from year's of drinking, but was found capable of helping his lawyers.

In the Windom case he was diagnosed as suffering from paranoid schizophrenia, depression and anxiety but the judge decided he was competent to enter his guilty plea.

Doctors say some people can be treated over time and become competent to assist in their own defense at a later date.

But, there's no one size fits all diagnosis because there's so many elements involved.