There are essentially are three different approaches to defense a person can take when facing drug possession charges. A person may use a procedural defense or may challenge the evidence in the case. There is also what is known as an "affirmative defense", which would include pointing out the legality in Ohio of using medical marijuana.
Procedural defenses often focus on illegal search and seizure. The Fourth Amendment protects people against this. An example could be a traffic stop in which a person does not consent to a search although if the drugs are in plain sight, this probably would not be a procedural violation. A person's attorney should also follow up on any crime lab analysis and make sure the drugs are not lost between the time of the person's detention and the trial. In the former case, the substance might not be drugs at all. All of these situations can be grounds for dismissing the entire case.
Some people may present evidence at the trial that the drugs belonged to someone else. Drugs might also have been planted or the person may have been a victim of entrapment. A person cannot use a medical marijuana defense in a federal court, but it might be successful at other levels depending on the particular circumstances. People may want to contact an attorney to discuss these options.
A conviction on drug charges can affect a person's access to financial aid for education, to some forms of housing and to some career fields in addition to the legal consequences. Therefore, the charges should be taken seriously even if the person only had a small amount. The person may also want to discuss the possibility of a plea bargain with the attorney if none of the above options seem viable.