The state dropped charges Friday against a former migrant worker who spent more than 21 years in prison for the poisoning deaths of his seven children, saying the evidence indicated the man probably did not commit the crime.

Dade County State Attorney Janet Reno said there was insufficient evidence to charge James Joseph Richardson, 53, with poisoning the rice and beans that killed his children.Retired Circuit Judge Clifton Kelly overturned Richardson's conviction April 25 in Arcadia, freeing the former fruit picker from Tomoka State Prison near Daytona Beach.

Richardson's case was reopened earlier this year after defense attorneys Ellis Rubin and Mark Lane made public confidential reports from an investigators file indicating that prosecutors withheld evidence from Richardson's trial attorney and may have abetted perjured testimony.

Richardson was sentenced to death row in 1967 for the death of his stepdaughter, Betty Jean Bryant, 8, one of the seven children who died. That sentence was reduced to life in prison after the U.S. Supreme Court ruled the death penalty unconsitutional in 1972.

"The evidence I have indicates to me that James Richardson probably did not commit this crime," Reno told reporters at her Miami office. "We will never be able to prove who did."