WEST PALM BEACH, Fla. -- A Florida teenager accused of bludgeoning his parents with a hammer believes he has "such a strong defense" he'll reach a plea deal to avoid a life sentence

But for now, 18-year-old Tyler Hadley has pleaded not guilty in the deaths last July of Blake and Mary-Jo Hadley. Police say Hadley threw a huge party at his parents' house after their deaths.

In jailhouse letters to friends and family, he expresses hope he can avoid a life prison sentence or be placed in a state hospital.

The teen repeatedly complains of depression in his letters, and says he cries daily and prays for forgiveness.

The letters are part of a batch of documents made public by prosecutors.

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  • Parents Killed Party

    This undated photo provided by the Port St. Lucie police shows Mary Jo Hadley. Hadley's 17-year-old son Tyler Hadley is accused of beating his parents to death with a hammer and then throwing a party. The bodies of his parents, Blake and Mary-Jo Hadley, were discovered early Sunday morning, July 18, 2011 after police received a tip. (AP Photo/Port St. Lucie Police)

  • Parents Killed Party

    This photo provided by the St. Lucie County Sheriff's office on Monday, July 18, 2011, shows Tyler Hadley, 17, of Port St. Lucie, Fla. Hadley is accused of beating his parents to death with a hammer and then throwing a party while their bludgeoned bodies were locked in the master bedroom. He is being held on two counts of first-degree murder in the deaths of his parents, Blake and Mary-Jo Hadley. (AP Photo/St. Lucie County Sheriff's office)

  • Parents Killed Party

    This drivers license photo provided by the Port St. Lucie, Fla. police department shows Blake Hadley. Tyler Hadley, the 17-year-old son of Blake and Mary-Jo Hadley, is charged in the killings of his parents, whom authorities say he bludgeoned with a hammer Saturday before hosting a party for dozens of friends. A motive remains unclear. (AP Photo/Port St. Lucie Police Dept)

  • Florida Teen Allegedly Kills Parents, Hosts Party Afterward

    Florida police say 17-year-old Tyler Hadley beat his parents to death with a hammer, hid the bodies and had a party at the crime scene.

  • Teen Allegedly Kills Parents, Then Throws Party

    17-year-old Tyler Hadley is accused of killing his parents with a hammer, hiding their bodies in a bedroom, then hosting a party at the crime scene.