I believe we can compare pattern evidence to medical opinion and that we’re both looking at the objective signs and or symptoms of what we’re dealing with.
The medical opinion most often associated with forensic science is probably that of a medical examiner. Informed by a breadth of other sciences, medical examination resides on the more subjective side of the spectrum, relying heavily on the experience of the practitioner to determine the cause and manner of death.
One of the first questions law enforcement wants answered is: when did this person die? There are hundreds of factors that can affect the process of answering this question. For instance, while rigor mortis (where muscles lock, stiffening the body) begins within two to six hours of death, ambient temperature and the deceased’s muscle build and exercise habits affect the timing of rigor mortis.
Many other time markers help shape the story. As the blood settles due to gravity, it gives the skin a reddish color. Additionally, body temperature, gastric contents, bodily fluids (like the fluid in the eye), and the developmental stage of insects found on the body can also be examined to determine how long ago the person died.
Each of the myriad factors is one part in developing an educated guess as to time of death, but in the end it cannot be determined with complete accuracy.
Cause and manner of death is another matter for the pathologist to assess. Manner of death is how the death came about and is based on the NASH classification: Natural, Accidental, Suicidal, Homicidal, while cause of death refers to what specifically killed the person. Opinions on manner can be much more evaluative and subjective than opinions as to cause. Sometimes it is clear cut and indisputable. In other cases, it may not be clear at all, so much so that the pathologist may rule it “undetermined.”
Although partially subjective, in competent hands the results of medical examination can be relied upon. As with other forensic disciplines, it is important for attorneys and judges to understand the limitations.