Dr. Ian Dunbar's Bite Scale Index
Level 1. Obnoxious or aggressive behavior but no skin-contact by teeth.
Level 2. Skin-contact by teeth but no skin-puncture. However, may be skin nicks (less than one tenth of an inch deep) and slight bleeding caused by forward or lateral movement of teeth against skin, but no vertical punctures.
Level 3. One to four punctures from a single bite with no puncture deeper than half the length of the dog’s canine teeth. Maybe lacerations in a single direction, caused by victim pulling limb away, owner pulling dog away, or gravity (little dog jumps, bites and drops to floor).
Level 4. One to four punctures from a single bite with at least one puncture deeper than half the length of the dog’s canine teeth. May also have deep bruising around the wound (dog held on for N seconds and bore down) or lacerations in both directions (dog held on and shook its head from side to side).
Level 5. Multiple-bite incident with at least two Level 4 bites or multiple-attack incident with at least one Level 4 bite in each.
Level 6. Victim dead.