When it comes to virtually any criminal charge it is important to face it head on and do what is necessary to build a defense against the charge. In most cases there are multiple approaches that can be taken. This is true where drug possession charges are concerned.
One defense that someone charged with drug possession might raise is entrapment. Since the crux of this defense is that the accused is induced to commit a crime, it would likely only be applicable in situations where a sting operation is implemented and the person facing the charges bought drugs that were provided by the state. Another defense along those same lines that might be used in this situation is that the drugs were planted. Here again misconduct on the part of authorities is involved.
A second approach has to do with how the drugs were handled following the arrest. First, they should be analyzed by a crime lab to confirm that they are in fact what law enforcement alleges. Similarly, at trial the drugs should be produced. Without the evidence there is no case.
There is always the defense that the drugs that got you into trouble in the first place are not yours. In other situations it can be asserted that the way in which the drugs were uncovered was unlawful. Called unlawful search and seizure, the drugs cannot be used as evidence at trial if the Fourth Amendment rights of the accused were violated.
Whether any of these approaches will work in a specific case depends on the circumstances surrounding the alleged crime. To help determine the best way to proceed, a criminal defense lawyer is beneficial.
Source: FindLaw, “Drug Possession Defenses,” Accessed Dec. 11, 2014