In Texas, free flowing blood can be wiped off the patient and then used for a BAC assessment. . .and if the blood drips onto hospital beds/chairs/furniture or the floor, the blood may be taken for BAC assessment.
And if the unconscious guy laying in a hospital bed, is not under any suspicion of any crime, is not bleeding, should the cop just knock the guy up a bit to cause some free flowing blood? Just because he can?