I was going to say it's rather icky that they made this movie during the time he was actually active...but your comment makes more sense of it.

Too bad forensics had not yet evolved sufficiently. He left material evidence everywhere, they just didn't have the technology and techniques to properly interpret the evidence they had. How many crimes these days are solved based on unique prints from boots/shoes including how a person's unique gate will create unique wear in the sole of the shoe so that, even among the same brand, and even size, of shoe, the prints can be differentiated? Zociac killer left a boot print and they couldn't even get a warrant to seize Leigh's military-style boot for an analysis.