Bill Cosby’s lawyers presented expert testimony about memory at a civil trial in California on Thursday as they tried to discredit a woman’s account of what she said was a sexual assault by Mr. Cosby some 47 years ago.

Dr. Deborah Davis, a psychologist and an expert in sexual communication, told the court that memories can fade over time, and a person can develop false memories based on details of unrelated events that occur later.

“Distortion of memory can be because of things like societal change or the #MeToo movement,” she said. “It can cause you to think about it differently and remember it differently.”

Dr. Davis, who also spoke on the issue of consent and on misunderstandings in sexual signaling, was one of three expert witnesses Mr. Cosby’s legal team was expected to bring forward as it tries to persuade a jury in the trial in Santa Monica that the woman, Judy Huth, fabricated an account of a sexual assault that she said happened in a bedroom at the Playboy Mansion in 1975.

Ms. Huth, 64, testified earlier this week that Mr. Cosby, now 84, had invited her to the Playboy Mansion, where he tried to put his hand down her pants and then forced her to perform a sex act on him.

Because Ms. Huth, then 16, was a minor at the time, the statute of limitations in the case was extended and set by the date at which Ms. Huth fully realized the psychological damage from such an event. She has testified that she did not recognize the impact of the episode until many decades later, when she was an adult.

She filed suit in 2014, but the case was delayed in part by Mr. Cosby’s criminal prosecution in Pennsylvania, where he was convicted in 2018 of having sexually assaulted Andrea Constand, a former employee of Temple University. That conviction was overturned last year on due process grounds.

The 12-person panel sitting for the Huth case is expected to begin hearing closing arguments in the next few days.

Only nine of the 12 jurors must agree on a verdict, and their decision must be based on a preponderance of the evidence — a different standard than that used in criminal trials, where the proof needs to be convincing beyond a reasonable doubt.

Still expected to testify as part of Mr. Cosby’s defense are another expert on memory and a medical professional who performed a psychological evaluation of Ms. Huth in recent weeks.

Earlier in the trial, a forensic psychiatrist brought forward to testify by Ms. Huth’s legal team said that traumatic memories from sexual assault were strongly encoded in a person’s brain, such that victims of such events could accurately recall the details of their trauma many years, even decades later.