The jury's suspicions of Casey Anthony's father played a role in the decision to acquit the 25-year-old Orlando woman of murder, the panel's foreman said.
George Anthony seemed to have "selective memory" during his testimony, juror No. 11 told Fox News Channel's Greta van Susteren.
"That, in itself, was something that I always kept in the back of my mind for every time that got up there," he said. "I was just kind of on guard for that."
The juror's name was not given during the interview in St. Petersburg, part of which aired Monday night during van Susteren's "On the Record" show.
The Pinellas County jury found Anthony not guilty of the major charges involving the death of her daughter, Caylee. The 2-year-old was last seen alive June 15, 2008.
The defense, in opening statements, said the toddler accidently drowned, that the death was covered up by George Anthony and that George Anthony sexually abused his daughter.
George Anthony denied the allegations during testimony, and no direct evidence was introduced to substantiate them. Most jurors did not consider the sexual abuse claims during deliberations, the foreman said.
"There was no evidence to back that so I could not really take that into consideration," he said. "I was going to let what he did up on the stand dictate how I felt about him."
However, the foreman, a teacher in his 30s, said George Anthony's many appearances during the trial left a lot of questions.
"There was a suspicion of him," he said. "That was a part of our conversation that we had of what I'd call round-robin topics that we had when we were doing deliberation. That was brought up."
He gave examples of George Anthony's testimony that concerned jurors:
"With the can, the selective memory, the way he handled the tow yard incident, River Cruz, the lady he could have had an extramarital affair with, it raised questions. It really did," juror No. 11 said.
The panel foreman said doubts about George Anthony involved his character as well as questions about his involvement in Caylee's death.
"Both for me," he said. "Character as far as the fact that he could be possibly lying, also the fact that his involvement was going to be in question because he was there. He was there on the 15th, he could tell you exactly when Casey and Caylee left. How do we know that that is right? It questioned a lot for us."
The reservations even went as far as to consider George Anthony was responsible for his granddaughter's death.
"We don't know," he said. "The suspicions were raised. We talked about it in the deliberation room."
Because of safety concerns, the names of jurors were sealed by Judge Belvin Perry during the case. A motion by media outlets to release the names is under consideration by the judge.