The most obvious instance when a defendant may move to dismiss an action, either civil or criminal is an instance in which, viewing the evidence presented by the state (or plaintiff) in the light most favorable to that side, the burden of proof has not been met. This means there is no issue of fact to be determined by the jury, therefore the case should be dismissed. Such a motion is normally presented after the state (or plaintiff) has rested its case in chief. One should advise the court that one has "a motion" without going into particulars, so that the jury can be sent from the room. Motions to dismiss are matters of law, not fact, and juries should not be influenced by hearing the motion argued. If the motion is denied, it should be renewed after the defendant has presented his case; and if the verdict is against the defendant, it should be renewed a third time. It is highly doubtful that a judge will grant such a motion on the second or third effort; however by renewing the motion, the defendant has preserved his right to appeal the judge's decision to an appellate court. If he has not preserved his motion, this particular ground for appeal is lost.
An example: I once represented a young man charged with arson. He allegedly had burned the mobile home which he had previously rented and had recently vacated. The state offered evidence of the fire, and testimony from an expert that the fire had been deliberately set. A third witness testified that he had seen a vehicle leaving the scene quickly after the fire; but could not identify the vehicle or the driver. The state then rested. There was no evidence connecting the defendant to the fire. Thus, viewing the evidence presented in a light most favorable to the state, there was no evidence that connected the defendant to the fire, and the judge granted my motion to dismiss.