Published: May 13, 2010 10:19 PM EDT

PALATKA, Fla. - The father of a missing Florida girl is negotiating a plea deal for a 15-year sentence on drug-trafficking charges in exchange for testimony against his ex-wife and her brother.

Attorney Terry Shoemaker said Thursday at a pretrial hearing that his client Ronald Cummings hopes to have the deal before trial begins July 19. Shoemaker said surveillance evidence of five undercover drug deals with Cummings was a significant factor in his seeking a deal.

Cummings, his ex-wife Misty Croslin and her brother were caught in a drug-trafficking sting that ended in January.

Eighteen-year-old Croslin was at home with Haleigh Cummings the night the 5-year-old disappeared in February 2009. Putnam County Sheriff Jeff Hardy now considers the case a homicide investigation.