Rule 21 - Transfer from the county for trial(a) For prejudice in the county. - The court upon motion of the defendant shall transfer the proceeding as to that defendant to another county whether or not such county is specified in the defendant's motion if the court is satisfied that there exists in the county where the prosecution is pending a reasonable probability of so great a prejudice against the defendant that the defendant cannot obtain a fair and impartial trial in that county.(b) Transfer in other cases. - For the convenience of parties and witnesses, and in the interest of justice, the court upon motion of the defendant may transfer the proceeding as to that defendant or any one or more of the counts thereof to another county.(c) Proceedings on transfer. - When a transfer is ordered the prothonotary shall transmit to the prothonotary of the county to which the proceeding is transferred all papers in the proceeding and any bail taken, and the prosecution shall continue in that county.De. R. Crim. P. Super. Ct. 21