Someone recently told me that they were staying at a friend's house when the police came to the home and executed a search warrant. The search revealed an extensive, indoor marijuana grow and both the resident and the guest were charged with cultivation. The guest asked me if he could be convicted of Marijuana Cultivation simply by being present in the home.
The fact pattern raises several interesting issues. One question is whether the grow operation was legal. Maine has a pretty good medical marijuana law, which allows an individual over 21 to be a primary caregiver who can be designated by up to five patients to supply them with marijuana through cultivating up to 6 plants per patient. It was not clear if the resident and patients had taken all the steps needed to properly designate the grow operator as the primary caregiver or if the number of plants exceeded the legal amount. Putting that question aside, the house was really asking about accomplice liability: where does the law draw the line between a criminal accomplice and someone who just happened to be there?
Maine Law title 17-A §57(3) defines accomplices. Generally speaking, an accomplice is someone who acts with the intent to promotes or facilitate the commission of a crime and in so doing aids or attempts to aid or agrees to aid someone else in planning or committing the crime. The commission of the crime has to be a foreseeable consequence of the person's action. So in part, the answer is simple: just being there is not enough. However, evidence that the guest took other action might make him look less like a bystander and more like a criminal. For instance, bringing the homeowner/cultivator a sandwich does, in a sense, facilitate his nutrition and thus his ability to cultivate marijuana. Still, that probably does not make the guest an accomplice because marijuana cultivation is not a foreseeable consequence of making a sandwich. Bringing over some gardening tools might be getting closer, bringing a bunch of potting soil is a bigger problem, supplying grow lights would be worse.
In the end, this is a question for the jury and their verdict will be based on what facts the prosecution can prove. The houseguest's state of mind and what they knew about the grow become very important. Since the prosecution can't call the defendant as a witness, they will need to rely on circumstantial evidence to try to prove what the houseguest knew and when he knew it. Somewhere between a sandwich and grow lights, there is a line; if he is on one side, he is not guilty, if he is on the other he can be convicted as an accomplice.