This should answer your question.

Breston (police dog pictured in the link below) uncovered a shipment of marijuana in heat-sealed Mylar bags, inside plastic-lined crates sealed with foam sealant, inside a closed storage garage.

Howstuffworks "How Police Dogs Work"

A dog's sense of smell is like 1000x greater then ours. There have been dogs that have smelled marijuana through a gas tank and gasoline and many layers of hard core plastic wrap and tape. If you let the weed sit in one spot long enough, the odor will permeate through any liquid, metal, glass, or material. Watch the video "never get busted again" and you'll see records of this by a former police dog trainer.

Odor permeates anything... but it does so over time. If you put tuna fish in a fresh ziplock bag (and make sure to use rubber gloves so you don't get *any* residue on the outside of the bag when sealing it) you will not smell it through the bag right away. But after a half hour or so you would be able to smell it through the bag. Odor permeates practically all materials over time.

The best thing to do if you want to drive with marijuana is to get rubber gloves and layer the weed in several layers of plastic, using the gloves to touch the bud and your uncontaminated hands to touch everything else (the bag seals, etc.). Then take the wrapped bud and put it in a thick nalgene bottle sealed as tight as you possibly can. I would think that would keep a dog from smelling it for a little bit... but not for long.

As far as your legal question, I would say prior convictions alone don't result in probable cause for a search. Legal disclaimer follows: I'm not a lawyer, just a law student providing the best legal information I have, one friend to another. I am in no way attempting to give you legal advice. ;-) In all seriousness, I wouldn't be surprised if a cop thought he had probable cause because of prior convictions. But you could fight that in court pretty easily, I would think.
jsn9333 Reviewed by jsn9333 on . dog smell can a dog detect marijuana smell, if u have it wrapped up tightly and sealed in an airtight glass jar? also, if i have a possesion and parephenilia charge record, is that automatic probable cause for a cop to search my vehicle even tho it was over a year ago? Rating: 5