Casey Anthony's attorneys showed photos of her daughter Caylee climbing a ladder into an above-ground pool at the family's home as her grandmother, Cindy Anthony, supported her from behind.
From the witness stand, Cindy Anthony testified that Caylee was able to open a sliding glass door that led to the backyard pool.
"Even at that point, she could even climb into the pool," Cindy Anthony said when shown a photo.
Casey Anthony's attorneys contend that Caylee drowned in the pool and that her mother didn't kill her.
Casey Anthony, 25, wiped away tears while a video of her playing with the girl was viewed by the jury during her mother's testimony.
Prosecutors have argued Casey Anthony suffocated her daughter in June 2008. She didn't report the girl missing for 31 days.
Later Friday, Casey Anthony's brother, Lee, testified about stains found in the trunk of his sister's car. Cindy Anthony also has testified about the stains, saying they were present when the family bought the car in 2000.
Prosecutors claim the child's body was in the car trunk and then dumped near the Anthonys' home in Orlando in a wooded area, where Caylee's remains were found nearly six months after she disappeared. They have presented extensive evidence of human decomposition in the car trunk, including stains.
Lee Anthony started crying on the witness stand when he recalled how he didn't go to the hospital for his niece's birth. He said he was angry at his sister and mother for not directly confiding in him about Casey Anthony's pregnancy.
On Thursday, Cindy Anthony's testimony directly contradicted prosecutors' theory that Casey Anthony was the one who made Internet searches about chloroform, a chemical compound that can be used to knock someone unconscious and also is found in human decomposition.
Earlier in the trial, a medical examiner testified that even a small amount of chloroform would be sufficient to cause a child's death.
Casey Anthony has pleaded not guilty to first-degree murder and could face the death penalty if convicted of that charge.