The Tapes Case

D and others are charged under the federal gambling statute with running a bookmaking operation that took bets on sporting events, primarily over the telephone. The evidence used to secure the indictment was derived from court-ordered electronic surveillance of some 3,000 telephone calls. The statute requires, among other things, a volume of at least $2,000 per day. At the trial an FBI agent with considerable experience in telephone interceptions testifies as to the mechanics of the wiretaps, the accuracy of the equipment, and the training of the monitoring agents. The prosecution then offers the testimony of an expert to the effect that the total daily dollar volume based on an analysis of the 3,000 calls was $899,855, with the lowest daily total being $8,395. D objects on best evidence grounds, arguing that it is necessary to play the tapes to the jury.

What ruling and why?