How to Catch a Serial Killer

How do you catch such a person, especially if there's 400 of them over the last century in the United States? This is like a needle in a haystack, right? Except a murderous needle. Yeah. So MO, the way you kill them, certainly the ritual of it, that's a big time giveaway. But what I found interesting was that the MO changes and evolves and actually grows more mature over time.