The standard of review set forth in Guzman v. State, 955 S.W.2d 85 (Tex. Crim. App. 1997), applies to claims concerning the voluntariness of oral and written statements. See Hernandez v. State, 957 S.W.2d 851, 852 (Tex. Crim. App. 1998) (per curiam). As a general rule, we afford almost total deference to a trial court's determination of the historical facts that the record supports, especially when the trial court's fact findings are based on an evaluation of credibility and demeanor. Guzman, 955 S.W.2d at 89. Likewise, we afford the same amount of deference to mixed questions of law and fact, if resolving those ultimate questions turns on evaluating credibility and demeanor. Id. However, we review de novo "mixed questions of law and fact" not falling within this category. Id. Determining whether a confession is voluntary must be based on the totality of the circumstances surrounding its acquisition. McCoy v. State, 713 S.W.2d 940, 955 (Tex. Crim. App. 1986). The State has the burden to prove the voluntariness of a confession. Gentry v. State, 770 S.W.2d 780, 789 (Tex. Crim. App. 1988).