The lucky penny: an illustration of the bullet rule

Dear Editor:

I enjoyed reading Drs. Engel's and Tien's vignette: "The lucky penny: an illustration of the bullet rule" in the January 10th, 2012 edition of the Journal. It illustrates important weaknesses in rules of thumb such as the "bullet rule" where the sum of the wounds found on examination and bullets found by radiographs should be an even number.

Unfortunately, the article goes on do describe other rules of thumb that are just as inaccurate. Without formal training in forensic pathology or ballistics, urgent care doctors may easily mistake bullet entries and exits using descriptors from Engel's and Tien's paper. Whereas these errors may not be clinically critical, the authors point out the ramifications to the criminal investigation that may follow will be important.

Their use of the word "typical" to describe entrance wounds with "muzzle marks" and "tattooing and soot" describes the less common injury with the weapon in close proximity or in contact with the patient. In order to form an imprint of the muzzle, enough gas must be injected by the gun into the patient in order to inflate the skin to slap against the muzzle of the weapon. The kinetic energy of unburned particles of gun powder is very low. Tattooing occurs at very close (1-30cm) but not contact range and on an unclothed target. In our institution, bullet wounds are rarely at contact or close range.

The article goes on to describe stellate lacerations of entry wounds. This is once again a description of a contact or near contact wound where gas injected into the wound exits quickly, splitting the skin on the entry side whose hole was sealed by the muzzle itself. Canada is still a country where long guns (rifles) are important for hunting, sport as well as rural and wilderness protection against animals. High velocity weapons may cause stellate exit wounds.

As a medical student, hearing of the very rare patient suffering a gunshot wound would cause significant numbers of my classmates and I to gather in the radiology suite to see images such as those presented by Engel and Tien. These injuries are becoming more common in Canada. Without formal training in wound identification clinicians should focus on finding and identifying all "wounds" and leave the CSI portion of the diagnosis to better trained experts.

Sincerely,

Robert Chen MD FRCPC (Anesth)

Anaesthesia and Critical Care Former Trauma Team Leader