What is the test for obtaining consent under the Fourth Amendment?

that one of the specifically established exceptions to the [search warrant] requirement... is a search that is conducted pursuant to consent.' [Citations.]" (People v. Wood (1999) 21 Cal.4th 668, 674.) "Where, as here, the prosecution relies on consent to justify a warrantless search or seizure, it bears the 'burden of proving that the defendant's manifestation of consent was the product of his free will and not a mere submission to an express or implied assertion of authority. [Citation.]'" (People v. Zamudio (2008) 43 Cal.4th 327, 341.)

"The voluntariness of the consent is in every case 'a question of fact to be determined in the light of all the circumstances.' [Citations.]" (People v. James (1977) 19 Cal.3d 99, 106 (James)?) In reviewing a ruling on a motion to suppress evidence: "We defer to the trial court's factual findings, express or implied, where supported by substantial evidence. In determining whether, on the facts so found, the search or seizure was reasonable under the Fourth Amendment, we exercise our independent judgment. [Citations.]" (People v. Glaser (1995) 11 Cal.4th 354, 362.)