For over a century, one question keeps coming up: could H.H. Holmes — America's first serial killer — also have been Jack the Ripper?

Books have been written. DNA has been tested. Holmes's own great-great-grandson spent years trying to prove it.

I looked closely at the evidence — and at the five most serious Ripper suspects on record. For each one, two questions: what does the evidence actually show, and does the psychology fit?

Because a killer's psychology is like a fingerprint. The way someone kills tells you something about who they are. And more importantly — who they're not.

What I found wasn't what I expected.