Those fluent in biochemistry may enjoy the details, but the gist of the article is summed up in the second paragraph:

It has often happened in murder trials that the guilt or innocence of the prisoner depended entirely on the ability of expert witnesses to determine whether or not certain stains were caused by human blood. Formerly, this was a difficult question to decide. The revelations of biological chemistry, however, have made the tests comparatively easy. In fact, it is not too much to say that the tests used nowadays to settle the question whether certain stain, be they new or old, were made by human blood, constitute an exact science.

This reminds me to recommend The Alienist, Caleb Carr’s murder mystery set in 1896 New York City, to those of you who have never read it. The protagonist uses newly developed techniques (like fingerprint matching, for example) to solve the crime. It’s a very good read.

BLOOD TESTS IN CRIMINAL CASES NO LONGER UNCERTAIN: Murderers Can No Longer Be Shielded by Doubtful Analysis, for the Newest Biological Chemistry Can Now Tell Human Blood Stains from Others. (PDF)

From March 26, 1911