ST. PETERSBURG, Fla. — An assistant state attorney described the scene where 5-year-old Phoebe Jonchuck was dropped into the water, and the suspect's defense team called it a case of insanity.

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The trial of John Johnchuck, charged in the 2015 death of his daughter, started Monday.

If he is found guilty, Jonchuck will spend the rest of his life in prison.  Otherwise, he'll got to a mental institution and likely never be released. 

The 12-person jury, which was seated Friday, heard from Assistant State Attorney Paul Bolan.

"The defendant takes her from the vehicle, turns and then lets go. Drops her from a height of about 70 feet into the dark water of Tampa Bay. The officer heard her scream on the way down," Bolan said.

It happened off the southbound approach to the Sunshine Skyway Bridge.

The motive, according to the state, is cut and dry. They said Jonchuck wanted to punish the mother of his child for moving on with a new boyfriend, rather than risk letting her get custody of the girl.

Jonchuck doesn't deny he dropped his daughter off the Dick Misner Bridge. But his defense team said he was in a state of pyschosis when he did it.

"It does not make sense," said a member of the defense team. "It will not make sense. You cannot try to force it to make sense.  Because it is insanity."

The defense said Jonchuck "loved Phoebe more than anyone."

The defense has the burden of proving that Jonchuck was insane when his daughter was dropped to her death.

 
While Jonchuck has a history of mental problems, successful insanity defenses are rare. 

Criminal defense attorney Kevin Hayslett, who is not involved in this case, told Spectrum Bay News 9 that these jurors will have to hear difficult details, see heart-wrenching photos, and ultimately set aside their emotions to come up with a verdict.

"This case is difficult because the judge has to ensure even if you've heard information about the case, can you put that aside and be fair and impartial, and only rely on the evidence that comes in the courtroom from witnesses?" Hayslett said.