The Barson family has filed a wrongful death lawsuit against Williams.
Williams' lawyer said on Thursday she expressed her "deepest condolences" but that it was an "unfortunate accident".
"I'm completely speechless. It's just - yeah, I mean, I'm just..."
She was focused enough on court against Mertens, but it quickly became clear the press conference wasn't going to be so easy to deal with.
An attorney for tennis star Venus Williams maintains the Florida vehicle crash that cost the life of a 78-year-old man was simply an "unfortunate accident".
"My heartfelt condolences go out to the family and friends of Jerome Barson and I continue to keep them in my thoughts and prayers", the athlete continued.
Williams claims that she entered the intersection while the light was green, but had to stop due to the traffic in front of her.
Palm Beach Gardens Maj Paul Rogers says the crash remains under investigation. Her next match is Wednesday against Wang Qiang.
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Venus Williams is being sued over a fatal auto crash in Florida last month which she was allegedly at fault for.
Asked about her feelings during such a hard period, she tried to keep her answers limited to tennis at first.
Williams's attorney Malcolm Cunningham, however, denied the player was at fault in the June 9 accident after media outlets, citing a police report, said she had run a red light.
Venus Williams tried to answer the question, but she couldn't.
Jerome Barson, a 79-year-old who was a passenger in his wife's vehicle, was injured and died two weeks later. In addition, police say there is no evidence that Williams was under the influence or distracted by an electronic device.
According to the police report of the accident, Williams was said to be driving around 5 miles per hour when another auto ran into hers.
Williams is now ranked 11th in the world and seeded 10th at the Wimbledon Open, which she has won five times.