No-knock warrants can only be justified in cases where the evidence sought can be quickly destroyed, such as a small amount of soluble or combustible material,

No-knock warrants can only be justified in cases where the evidence sought can be quickly destroyed, such as a small amount of soluble or combustible material, or written material (especially on "flashpaper"). In the Branch Davidian raid in 1993, Janet Reno's crew had sought a no-knock warrant, but they were denied because the objects of the warrant (fully automatic guns and conversion kits) can't be quickly destroyed. They used no-knock tactics anyway.