420 is police code for murder in only one state. Furthermore, there is no knowledge of who coined the term in this clever origin story. When did Nevada start using 420 as code for murder? Why would murder and marijuana become linked before the penal code for drug possession and marijuana? This argument seems unlikely, has a lot of holes, and is little known. The fact of the matter is 420 is not police code for smoking cannabis in any state. 
This convoluted explanation of murder being the bridging link between 420 and marijuana has no evidence to back it up, and sounds more like a constructed history lesson than an actual origin story.