Published: Feb 25, 2013 5:25 PM EST

LEE COUNTY, Fla.- Trial is under way for a Lee County dad accused of beating his 4-month-old son to death. Jury selection began this morning.

Deputies say Ryan Costello beat and strangled his son, Darwin. Prosecutors tell WINK News they not only want to prove he killed his son, but that his alleged drug dealing was part of the reason he didn't get help for the baby.