Beneath the surface

    It would be fair to say that assault investigations are a daily occurrence for most law enforcement agencies. Techniques of observation are paramount to all levels of law enforcement investigation involving assaults which our profession is often called to investigate. Knowing what to look for and how to look for physical evidence helps to verify assault claims and has a major impact on how we proceed with cases. How can law enforcement document injuries that are internal or even advise victims they need to seek medical treatment if our abilities are limited? There may be a way in the near future where we could see the unseen.

 History of thermography

Law enforcement is familiar with the use of infrared imaging, as it is used with night vision equipment and for surveillance operations. But could it be used for something more? Thermology is the study of heat, but Medical Thermography is the study and evaluation of skin temperature. By mapping the distribution of heat it's easier to visualize where abnormalities are localized that may indicate a problem. Those changes can also be used to detect the cause of an underlying problem(s). It’s noted that as far back as 2,400 years ago the Greek physician, Hippocrates, used the drying speed of wet mud applied to the body to indicate problems that needed further examination.* He is quoted as saying “In whatever part of the body excess heat or cold is felt, the disease is there to be discovered.” Crude thermometers were created in the 1500’s and, Sir William Hershel, is credited with the discovery of the infrared spectrum in the 1800’s.*

Techniques and equipment used in thermography greatly advanced between the 1920s through the 1970 and so much so that the United States Department of Health, Education, and Welfare (now the U.S. Dept. of Health and Human Services) deemed thermography as being beyond experimental. This technology has been used with great success with equine veterinarians since 1964. Likewise, thermography has been used clinically on humans for approximately the last 40 years, especially in the area of musculoskeletal medicine and breast health risk assessment. The American Academy of Thermology has established a number of guidelines for use in clinical evaluations that include patience assessment, patient consultation, examination procedures, equipment parameters and review of findings from images.*

Examinations of this level require specialized training that far exceeds what patrol officers or investigators would know. It is important to mention, however, that officers could direct assault victims to appropriate medical services if indicators are present that an assault did occur. This is especially true in strangulation cases where the risk of death is high even hours or days after a strangulation event.   

What is this method capable of?

Infrared thermography looks at surface temperature. It cannot see inside or through structures of the body. Heat from the skin’s surface is what can be detected. The human body exhibits what is called “contralateral symmetry” of temperature.* That is to say, there is a balance of temperature in the body that comparatively should be the same on opposite sides. For example, when comparing one limb to another, it should be symmetrical in its temperature ranges. An asymmetrical pattern in one limb as compared to another can indicate a problem. Thermal changes can indicate pain or injury in the body among both equine and human patients. Notable uses for thermography are for vascular problems, muscle injury, inflammation, and nerve injury.* As cited by the American Academy of Thermology, medical disciplines that have an interest in using thermography include neurology, neurosurgery, physiatry, pain specialists, orthopedics, occupational medicine, vascular medicine, oncology, and dentistry. (Physiatry is the study of pain and courses of its treatment). Technology today provides us with full vibrant colors of temperature variations, and not just the white, black and gray images commonly seen in decades past.

Tools currently available to law enforcement

There are many companies that manufacture handheld thermal imaging devices of various sizes, costs and resolutions. For daily law enforcement use, small handheld units would seem the most appropriate, especially when investigating assaults. Some units range from as little as $250 for Apple and Android cell phone camera adapters to larger commercial hand units costing tens of thousands. Budgets are always a concern, but any agency wanting to purchase such a unit would be advised to acquire one with the best resolution they could afford. Some of the more common manufacturers are FLIR Systems and SEEK Thermal all which have various handheld models to pick from. The basics of thermal cameras operation are that they detect infrared heat, convert it into an electronic signal that is then processed into an image.

Would it be beneficial to detect the subtle internal and hidden signs of assault to include strangulation? The answer of course is, yes, both for medical intervention and investigative purposes. Thermography has been used for fugitive searches, rescue operations, surveillance, officer safety and hidden compartment detection; however, there have been no easily found studies on its use investigating assault cases. As an example; strangulation injuries in domestic violence assaults are often missed. Contrary to popular belief, non-fatal and even fatal strangulations leave very few, if any, signs of external injury. Frequently, the only indicators of strangulation are internal and therefore harder to detect without proper training. By contrast, choking is an internal blocking of the airway by a foreign object, but this is often used incorrectly to describe strangulation. Subtle signs and symptoms of strangulation are: headache, sore neck, sore throat, trouble swallowing, raspy/hoarse voice, breathing difficulty, vomiting, petechial hemorrhage, loss of bowel control and loss of memory. A sore throat and/ or voice changes are present in 50-70 percent of evaluated cases. Repeated acts of non-fatal strangulation lead to long term behavioral, neurological and psychological disorders.

Victims of strangulation can die hours or weeks later from a strangulation event if immediate medical intervention is not sought. A published study through the Journal of Emergency Medicine (October 2008, 35(3), pages 329-335) showed that if a woman survives strangulation even once, she is 700 percent more likely to be strangled again and 800 percent more likely to be killed later. The lack of physical evidence in strangulations has caused many to treat it as a minor incident, when in fact, they are some of the most lethal cases we will deal with.

It cannot be more strongly emphasized that thermal imaging in the hands of law enforcement can be used as an “indicator”, but should not be used to diagnosis or definitively conclude evidence of injury.  Indicators of injury accompanied by other known information about an assault should cause officers to investigate further using medical experts and at minimum advising any victim they should consider medical evaluation. In regard to non-fatal strangulation events, victims need immediate medical evaluation at a hospital because long-term medical complications and fatal events can occur hours or weeks after a strangulation event. Technology currently available could make it possible for officers to document indicators of strangulation and other assaults. What do professionals in their fields of study say about the possibility of using handheld thermology cameras to detect hidden strangulation injuries?  Kenneth Marcella, is a well-known veterinarian in Georgia who uses thermology with horses. He says “Thermal imaging can pick up injuries well before being visible on ultrasound.” Doctor Robert Schwartz, the chairman of the American Academy of Thermology, adds "I am rather excited about evaluating the use of thermal imaging by law enforcement for domestic violence and strangulation cases. With proper image acquisition and palette configuration these applications are quite plausible. It is possible that strangulation cases may require a different set up for detection than that used for other domestic injuries, however I anticipate that it should be relatively easy to accomplish the same."

Certainly, if this handheld technology could be put to good use in domestic violence cases it could be used in child abuse cases and vulnerable adult abuse cases as well. There are a number organizations who are currently exploring the validity of using this technology in assault cases.

It is important to note that the use of thermal cameras in assault cases should be used as an “indicator” tool and not used to draw definitive conclusions beyond the officer’s training and experience. Let the medical professional conduct more specific exams if indicators are present that injury is possible.

 It’s difficult to see what the future holds, however, in time we might be able to see what lies beneath the surface of assault victims.

Special note:  Officers who are interesting in free online strangulation investigation training can go here http://www.strangulationtraininginstitute.com/training/online-strangulation-training/