A lawyer for Muriel and Jim Sitton said she plans to appeal Monday's decision, the Palm Beach Post reported.
The Sittons' 6-year-old daughter was one of four people shot and killed by Paul Merhige during a 2009 rampage at his parents' home in Jupiter. Merhige, 37, who pleaded guilty and is serving seven consecutive life sentences, also killed his two sisters, Lisa Knight and Carla Merhige, both 33, and Raymonde Joseph, 76, Muriel Sitton's mother.
Palm Beach County Circuit Judge Meenu Sasser has already dismissed a lawsuit by Lisa Knight's husband. She gave the same reasons for blocking the Sittons' actions.
"Similarly, no Florida court has imposed liability on parents of an adult child where financial dependence was coupled with allegations of insanity or mental deficiency," she said.
The Sittons' argued that Merhige's parents knew he could be violent and had invited him to Thanksgiving dinner without warning them.