Mr Dos Santos and Ms Williams, both international athletes, believe they were racially profiled during a “disturbing" July 4 2020 encounter with five Metropolitan Police officers who followed them as they drove to their west London home from training with their then-three-month-old boy in the back seat of their Mercedes.
Mr Dos Santos claimed officers approached his car aggressively with “glass cutters and batons raised" when he pulled up outside his house before they briefly detained him and his partner.
Body-worn footage of the encounter was released on Thursday in connection with a disciplinary hearing in south-east London, where the five officers could be sacked if gross misconduct is proven.
In the footage of the stop, Ms Williams could be heard to tearfully tell police: “My son is in the car - I need to look after him,” as her partner Ricardo Dos Santos was handcuffed.
Minutes later, she too was detained, as Acting Sergeant (A/PS) Rachel Simpson suggested the couple had “antagonised" the police and may have “something to hide".
At one point in the footage, the infant can be heard screaming as A/PS Simpson leaned into the back of the car to “check around the baby seat" before allowing Ms Williams to collect her son.
The pair were searched for drugs and weapons, but nothing was found and the couple were released shortly after.
In a clip released by the police watchdog, officers can be heard to tell the top athlete: “You shot off from the police at speed, you made a definite attempt to avoid us, the driver has, which makes us suspect there’s something in the car there shouldn’t be.”
Ms Williams can be heard repeatedly denying any wrongdoing, rejecting police claims that the vehicle ran a red light to avoid officers.
“This is ridiculous, we live here,” Ms Williams can be heard to say, adding: “Go and have a look, this is ridiculous. You were already following us, as soon as we made that turn … We haven’t gone through a red light.”
.A/PS Simpson, Pc Allan Casey, Pc Jonathan Clapham, Pc Michael Bond and Pc Sam Franks deny all charges against them, which include allegations that they breached police standards over equality and diversity during the stop-and-search.
The panel previously heard from Mr Dos Santos, 28, a Portuguese competitor in the 400m sprint at the Tokyo 2020 Olympics, who claimed he had been left "traumatised" by several encounters with police who stopped him without reason.
He told the panel he was "afraid" for the safety of his partner and child when the police van began following them before pulling them over.
At the hearing on Thursday, Ms Williams denied suggestions from James Hines, A/PS Simpson’s lawyer, that her partner could have acted differently to avoid police attention, insisting that "he can’t change the colour of his skin".
She said: "It isn’t easy constantly being pulled over for no reason - he’s been pulled over so many times.
"When it gets to 10 times I feel his frustration. It’s difficult."
When asked by Mr Hines why she had never been pulled over by police, Ms Williams said: "I am a female and he (Mr Dos Santos) is a black male and black males are 10 times more likely to get stopped."
A/PS Simpson and Pcs Clapham, Bond and Franks also face allegations that their actions amounted to a breach of professional behaviour standards in relation to the use of force.
They are said to have failed in relation to their levels of authority, respect and courtesy, as well as in their duties and responsibilities.
Pc Casey is also accused of breaching professional standards in the way he carried out his duties and responsibilities or gave orders and instructions.
It is also alleged that the honesty and integrity of Pcs Casey, Clapham, Bond and Franks breached professional behaviour standards.
The six-week hearing continues.