Williams and Dos Santos were stopped while driving in Maida Vale, London, on 4 July 2020, as they returned from training with their baby in the car.
The panel found as unproven the claim that the race of the athletes had played a role in their treatment.
The panel chair, Chiew Yin Jones, said they accepted that Dos Santos, who was regularly drug tested, did not take or possess drugs.
She said: “Given the breach of the standards of honesty and integrity, within an operational context, arising as it did during the course of an encounter with members of the public in which coercive powers were used, the panel found that conduct of PC Clapham and PC Franks amounted to gross misconduct as the breach was so serious as to justify dismissal.”
Jones said Clapham and Franks had been “untruthful” in their account that they smelled cannabis and then suspected the person responsible was Dos Santos. Jones said it led to the officers being “trapped in a lie”, and there was no objective basis for believing Dos Santos had cannabis in his car or person.
The case was brought by the director general of the Independent Office for Police Conduct.
Opening the hearing, the body’s counsel, Karon Monaghan KC, said: “The director general will say that not only did the officers lie about smelling cannabis, they did so because Mr Dos Santos was black.”
The car driven by the black athletes was a Mercedes, and officers had claimed it was the type of vehicle driven by gang members, thus contributing to their suspicions.
Monaghan said: “It was obvious that she [Williams] was with her partner and son rather than all being members of a gang.”
Both athletes were handcuffed during the stop.
The panel acquitted all officers of gross misconduct over their decision to stop the car the athletes were in, and the decision to handcuff them.
