Most emergency departments do not see much penetrating trauma. But it is helpful to be able to learn as much as possible from the appearance of these piercing injuries when you do see them. This post will describe the basics of reading stab wounds.

Important: This information will allow some basic interpretation of wounds. It will not qualify you as a forensics expert by any means. I do not recommend that you document any of this information in the medical record unless you have specific forensic training. You should only write things like “a wound was noted in the midepigastrium that is 2 cm in length.” Your note can and will be used in a court of law, and if you are wrong there can be significant consequences for the plaintiff or the defendant. This information is for your edification only.

1. What is the length of the wound? This does not necessarily correspond to the width of the blade. Skin stretches as it is cut, so the wound will usually retract to a length that is shorter than the full width of the blade.

2. Is the item sharp on one side or both? This can usually be determined by the appearance of the wound. A linear wound with two sharp ends is generally a two sided knife. A wound with one flat end and one sharp end is usually from a one-sided weapon. The picture below shows a knife wound with one sharp side.

3. Is there a hilt mark? This can usually be detected by looking for bruising around the wound. The picture below shows a knife wound with a hilt mark.

4. What is the angle? If both edges are symmetric, the knife went straight in. If one surface has a tangential appearance, then the knife was angled toward that side. You can approximate the direction of entry by looking at the tangential surface of the wound edge. In this example, the blade is angling upward toward the right.

5. How deep did it go? You have no way of knowing unless you have the blood stained blade in your possession. And yes, it is possible for the wound to go deeper than the length of the knife, since the abdominal wall or other soft tissues can be pushed inwards during the stab.

Determining The Age Of Bruises

On occasion, you may encounter a patient who has bruising and wonder how old the injuries are. Or there may be several bruises and you would like to know if they occurred at different times. This becomes especially important when dealing with injured children in whom there is a suspicion of abuse.

Bruising occurs when blood leaks from blood vessels into the skin and subcutaneous tissues. If the skin and soft tissues are firm, bruising is not as apparent. In areas where the skin and soft tissues are loose, such as the peri-orbital areas and scrotum, bruising is visible early and may be extensive. The elderly tend to bruise easily because both the skin and subcutaneous tissue are very thin and friable.

A predictable series of color changes occurs with most bruises. During the acute phase, the color is usually reddish and the area may be raised and tender. After about 2 days, the color turns purple and any swelling usually disappears. Over the next week, the color changes to green and yellow as the heme metabolizes. Finally, the color fades and by two weeks most evidence of the injury is gone.

The table above is a key to estimating bruise age. However, this is not an exact science! A number of studies have been performed showing that examiners given photographs of bruises of various ages were not terribly accurate. Fresh and intermediate bruises were identified fairly accurately, but not so for older bruises.

The trauma professional may find it helpful to use these guidelines when trying to decide if there are both fresh and older bruises present. This may indicate that an older adult may be suffering from frequent falls, or that a child needs to be evaluated for abuse.

Reference: Estimation of the age of bruising. Arch Dis Childhood 74:53-55, 1996.

Most emergency departments do not see much penetrating trauma. But it is helpful to be able to learn as much as possible from the appearance of these piercing injuries when you do see them. This post will describe the basics of reading stab wounds.

Important: This information will allow some basic interpretation of wounds. It will not qualify you as a forensics expert by any means. I do not recommend that you document any of this information in the medical record unless you have specific forensic training. You should only write things like “a wound was noted in the midepigastrium that is 2 cm in length.” Your note can and will be used in a court of law, and if you are wrong there can be significant consequences for the plaintiff or the defendant. This information is for your edification only.

1. What is the length of the wound? This does not necessarily correspond to the width of the blade. Skin stretches as it is cut, so the wound will usually retract to a length that is shorter than the full width of the blade.

2. Is the item sharp on one side or both? This can usually be determined by the appearance of the wound. A linear wound with two sharp ends is generally a two sided knife. A wound with one flat end and one sharp end is usually from a one-sided weapon. The picture below shows a knife wound with one sharp side.

3. Is there a hilt? This can usually be detected by looking for bruising around the wound. The picture below shows a knife wound with a hilt mark.

4. What is the angle? If both edges are symmetric, the knife went straight in. If one surface has a tangential appearance, then the knife was angled toward that side. You can approximate the direction of entry by looking at the tangential surface of the wound edge.

5. How deep did it go? You have no way of knowing unless you have the blood stained blade in your possession. And yes, it is possible for the wound to go deeper than the length of the knife, since the abdominal wall or other soft tissues can be pushed inwards during the stab.