The parents of a 14-year-old boy slain in 2004 by his best friend in a middle school bathroom are urging a judge to keep the killer locked in prison for life.

Jaime Gough's parents said in a letter to Miami-Dade Circuit Judge John Schlesinger that they believe Michael Hernandez remains a threat to society. The letter was read Wednesday at the opening of a three-day hearing on whether Hernandez deserves a sentence other than life.

The new hearing was mandated because the U.S. Supreme Court ruled in 2012 that juveniles could not automatically be sentenced to life without chance of parole. The decision was later made retroactive to older cases such as that of Hernandez, now 26.

Trial evidence showed Hernandez was obsessed with becoming a serial killer as a teenager.