concluding that the defendant manifested voluntary consent when he responded to the officer's request to search his van by, without speaking, removing the keys from his pocket, unlocking the door, pressing the door release and opening the door, and then stepping back to allow the officer's entry

affirming trial court's determination that, where officer asked the defendant, "Would you please open the door [of the van]?" the defendant's consent was voluntary

considering whether motion to sever, if made, would have succeeded

noting that evidence is irrelevant if it has "no logical connection to a fact or issue"

noting that considerations in voluntariness analysis include whether the person giving consent is the subject of an investigation