Fingerprints and blood are commonly gathered and tested in crime scenes today. But 100 years ago, this was new technology.
…if detectives were only trained scientifically, not merely in logic, so as to reconstruct a crime with proper attention paid to theory and fact, but also in chemistry, physics, and other sciences, there would be less need of expert testimony at criminal trials…
If the article interests you, definitely read Caleb Carr’s novel The Alienist, about a New York City murder investigation around the turn of the last century.
SCIENTIFIC DETECTIVE WOULD END EXPERT TESTIMONY: Head of Scotland Yard’s Bureau of Identification Urges Training of Sleuths — What Finger Print System and Blood Study Have Done. (PDF)
From July 2, 1911