|My DNA. No wonder I can't think straight|
These days the whole police business is far more professional. All officers are very aware of the need to preserve evidence at all costs. A footprint in mud will not last long on a rainy day. Bigger and bigger databases of DNA and fingerprints provide more chances of a forensic answer to that whodunnit question. In Shannon's Law both DNA and prints play significant silent roles.
Dr Edmond Locard (1877-1966) is not a household name like Sherlock Holmes, even though he really existed. He was essentially the Sherlock of France. To me he is the philosophical inventor of forensics. His principle was that "Every contact leaves a trace".
It's amazing what you stumble across as you research a novel. I was fascinated to find that in Mark Twain's 1883 story "Life on the Mississippi" a suspect was identified by fingerprints.
Emma Thinx: Love needs no contact to leave a permanent trace