In a search warrant application, what is the effect of a judge's finding on a police knock-notice?

In the present case, the trial court (magistrate) found no exigent circumstances existed to excuse the officers' duty to comply with the knock-notice requirements, as the officers did not know that drugs were being flushed or otherwise destroyed, or that anyone in the house was arming himself or herself or attempting to flee. Of course, this finding, to the extent it states a legal conclusion, is not binding on us. "In reviewing a ruling on a motion to suppress evidence, we defer to the trial court's findings of fact, whether express or implied, if those findings are supported by substantial evidence. We independently determine the relevant legal principles and apply those principles in evaluating the reasonableness of the search based on the facts as found by the trial court." (People v. Mays, supra, 67 Cal.App.4th at p. 972, 79 Cal.Rptr.2d 519.)