Published: Nov 07, 2012 6:33 PM EST
Updated: Nov 07, 2012 6:48 PM EST

LEE COUNTY, Fla. - Fatal family connections. Tonight, we're taking a look at three homicide cases where family members are accused of killing their dads or grandfathers.

Garrett Kern, Clinton Drake and Leroy Taylor. Each is a son or grandson who allegedly killed his elderly father or grandfather. And while each case is different, the patterns intertwined in all of them are disturbingly similar.

You're looking at the faces of three men accused of doing the unthinkable.

Dr. Duane Dobbert is a 41 year veteran of the criminal justice profession, and forensics professor at Florida Gulf Coast University. He is well versed in profiling kids, or adults, who kill their own blood.

"The greatest majority of the cases of parentcide is where we have, children and adults, are severely emotionally impaired or mentally ill," he said.  

Garrett Kern was the 23 year old accused of strangling his 80 year old step-grandfather to death, then dumping the body in a wooded area of Cape Coral last November.  

A month later, 19 year old Clinton Drake of Clewsiton was accused of beating his grandfather with a hammer several times, then slitting his throat with a knife.   The 84 year old's body was found abandoned in his car near the Midpoint Bridge at a very busy intersection.

This July, police say 52 year old Leroy Taylor junior beat his 91 year old war veteran father to death, and then threw gasoline on the body.  

The first similarity? The methods of killing are very personal. Each father or grandfather was killed in an up-close manner, strangled, beaten and bludgeoned.

"Finally, it gets to a point where they just strike out. And most of the cases we see its a point of rage. That: they just can't do it anymore," said Dr. Dobbert  

The next similarity? Dr. Dobbert says often, suspects in cases where a child kills a parent display signs of violence against others. In the cases of Garrett Kern and Leroy Taylor, both an ex-wife, and an ex-girlfriend say the two men relied heavily on drugs and alcohol, and were physically violent against them.

Only WINK News got these exclusive interviews.  

"It would be good for like a year an he would go right back to the violence again. When he would start to drink again, is when it would really be...you know, drinking and drugging. 

That's when it would take a turn for the worse," explained Leroy Taylor's ex-wife, who doesn't want her identity released.  

"He's angry, he's violent, he's an Oxycontin user, and once he started to use needles, then it got too big of a problem for me to handle," explained Robyn Schmittling, Garrett Kern's ex-girlfriend.  

Another similarity is the tension between a suspect and a victim in the weeks leading up to a homicide. "I know Garrett would have harmed him. If he did it probably was over money," said Schmittling.  

In the courtroom, Clinton Drake was hauled away after a sudden outburst. Police say Drake admitted to killing his grandfather.. after they got in an argument.  

In the case of Leroy Taylor, police reports indicate he depended on his father for money. But his father, said he no longer wanted to support his son.  

"Just angry. Coming out all at once. And it's built up. It's built up over the course of time and they finally lose their ability to use cognition to evaluate alternative behaviours," said Dr. Dobbert.  

Dr. Dobbert says the patterns of behavior including domestic violence, a change in mood, and aggression are tools for finding out if someone needs professional help, before they make a decision to take a life.

All three men are behind bars, charged with second degree murder. None of them has been to trial.