The discovery procedure involves the exchange of information between the prosecutor and defendant in a criminal matter prior to trial. There are state and federal rules of procedure, depending on the state or federal nature of the crime, that apply to the discovery process. Examples of things sought in discovery are alibi witness statements, samples taken at the scene of the crime, and codefendant statements. Failure to comply with a valid discovery request may lead to sanctions or exclusion of witnesses at trail. Certain things, such as work product, which is material that reflects an attorney's impressions, conclusions, opinions, or legal research or theories, are exempt from the discovery process.