A motion to compel can be submitted in both the criminal and civil context. It is a request from one party for the opposing party to reveal or turn over evidence that is considered material and pertinent to the pending case. In the civil context, both parties are required to turn over all evidence -- if attorney-client privilege does not apply -- to be used in the case. In the criminal context, the same is required, and parties are constitutionally required to turn over any exculpatory evidence under Brady v. Maryland.
Preference Against Motions to Compel
Courts are loathe to deal with discovery conflicts between parties. It is expected that attorneys and parties will be able to work out differences between them. In fact, nearly every state civil procedure code requires parties to make a diligent effort to recover documents from each other before involving the court. Motions to compel should be used very sparingly, and hardly ever more than once in the same case.
Filing Motion to Compel
If a party has made diligent efforts to compel discovery and the opponent either refuses to comply or cites a defense, the proponent (person seeking discovery) may draft a motion to compel and submit it to the court. The motion must inform the court of the precise document or piece of evidence to be recovered, and why it is important. Motions to compel must regard evidence that is material and pertinent to the case, and they cannot be collateral. The motion must be filed within the same court where the action is pending.
Answer to Motion to Compel
Within a designated amount of time, the opposing party must answer the motion to compel. The opponent may cite attorney-client privilege, undue embarrassment to the client, immateriality, or any other legally sound reason why the evidence should be excluded from discovery. The judge will probably ask to review the evidence creating the conflict, and she will do so privately in chambers. The judge will apply the rules and standards of the jurisdiction to determine whether the evidence should be turned over. If the motion to compel is granted, the opposing party may choose to appeal that ruling or to turn over the evidence immediately.
Appeal of Motion to Compel
Some states allow parties to appeal a trial court's decision to grant or deny a motion to compel. These are known as "interlocutory appeals," as they may be raised in the higher court before a trial even begins. An appeal of a granting or denial of a motion to compel is often difficult, as most jurisdictions will not disturb the ruling unless the ruling is arbitrary or clearly unreasonable. Generally, as long as the trial judge allowed the parties a hearing and considered all the evidence, an appellate court will not disturb the ruling.