Does a defendant have to prove that he gave consent to a search of his vehicle during a search?

Defendant further argues that if he did consent, his consent was "clearly not the product of his free will but rather his submission to the officers' express physical and oral assertions of authority." There is no indication that defendant's consent was not voluntary. Furthermore, the court heard the evidence and apparently determined that it was voluntary. (People v. James, supra, 19 Cal.3d at p. 107.) On the record before us, we conclude that the officers' testimony constituted sufficient evidence that the search of the vehicle was made with defendant's consent.