Solving murders in the 1920s must have been very hard. Obviously there was no such thing as DNA, but even fingerprinting was relatively useless because there was no national database of criminal fingerprints to match with. Unless you had a suspect in prison and some fingerprints on a murder weapon to match his, there was not much that fingerprints could do to prove guilt. Ballistics was in its infancy. Crime labs were nonexistent: Los Angeles opened the first American police crime lab in 1923 with a few part-time employees. Other major cities like New York didn’t set up such places until the mid 1930s. Tracing a fleeing suspect was next to impossible. Of course, there were no social security numbers or credit cards to help, and virtually no communication between police departments within a particular state, let alone between different states across the country. A murderer who left the area was gone forever, unlikely ever to be found, even if he didn’t bother to change his name. How would anyone know where to look? (“Gee, I think we should check the phone book in Duluth.”) It’s not surprising that 2/3 to 3/4 of all murders in the Twenties were unsolved.