Lots of people claim to have been in Northern California bin the 1970's, when Keith Bontrager, Gary Fisher, Joe Breeze and other mountain bike pioneers were barreling down fire trails in Marin and Sonoma County.
I wasn't there, so I'm not going to try to settle the question of who "invented" mountain bikes or mountain biking. But as with anything in which the earliest developments weren't--and probably couldn't have been--documented, a lot of legends and folklore have arisen.
From a couple of people who probably were there, I've heard that some folks who bought some of the early mountain bikes that were made for the purpose (as opposed to the DIY machines Bontrager, Fisher, Breeze and their peers fashioned from salvaged baloon-tired bombers) used their rigs to transport what was often called "California's biggest cash crop". And they weren't talking about wine grapes or almonds.
Of course, that cash crop is now essentially legal in the Golden State and in other places. That, like the end of Prohibition, has put smugglers and bootleggers out of business. But, as in most places, there are other substances that aren't legal. And there is a demand for those substances, which means that some folks will try to make a living by transporting them.
(Disclosure: When I was a bike messenger, I found myself making repeat trips to questionable locations with small envelopes and packages. I didn't ask or tell.)
And, yes, some will transport them by bicycle. That, apparently, is what Terrent Dowdell was trying to do. Now, the police claim they stopped him for not having "a reflective light" on the front of his bicycle. I also couldn't help but to notice that Mr. Dowdell is, well, black--in Columbus, Georgia.
Whatever the constables' motivation, they found "drug related items" and arrested him for possession of marijuana and heroin "with intent to distribute."