lists are references use copy

code/game/atoms.dm

@@ -506,7 +506,7 @@
 
 /atom/proc/clean_blood()
 	. = blood_DNA? TRUE : FALSE
-	blood_dna = null
+	blood_DNA = null
 
 /atom/proc/wash_cream()
 	return TRUE

code/game/objects/items/stacks/stack.dm

@@ -399,11 +399,14 @@
 		. = ..()
 
 /obj/item/stack/proc/copy_evidences(obj/item/stack/from)
-	blood_DNA = from.blood_DNA
-	fingerprints  = from.fingerprints
-	fingerprintshidden  = from.fingerprintshidden
-	fingerprintslast  = from.fingerprintslast
-	//TODO bloody overlay
+	if(from.blood_DNA)
+		blood_DNA = from.blood_DNA.Copy()
+	if(from.fingerprints)
+		fingerprints = from.fingerprints.Copy()
+	if(from.fingerprintshidden)
+		fingerprintshidden = from.fingerprintshidden.Copy()
+	if(from.fingerprintslast)
+		fingerprintslast = from.fingerprintslast.Copy()
 
 /obj/item/stack/microwave_act(obj/machinery/microwave/M)
 	if(istype(M) && M.dirty < 100)