evidence in connection with the officer's rebuttal testimony.  Finally, counsel for Wallace introduced parts of the recordings which tended to exculpate Wallace.


5
Appellants Wallace and Donohue2 urge that the recordings were inadmissible because they were seized in violation of the Fourth Amendment and the law of the State of Maryland where most of the surveillance took place.  Appellants further claim that obtaining recorded admissions through an informer after Barnes had implicated them before the grand jury violated their Sixth Amendment right to counsel.  Finally, they allege that the decision to sue the recordings after some of them had testified at the trial could not possibly afford them the reasonable notice promised in the pre-trial agreement.

A.  FOURTH AMENDMENT CLAIM

6
Appellants argue that the Supreme Court's ruling ineven if it was obtained in violation of state law.


8
We believe that the surveillance in this case was undertaken by a federal investigating agency within the meaning of the statutory exception.  The violations of law investigated and prosecuted arose under the federal conspiracy and District of Columbia bribery statutes, both offenses against the United States which are prosecuted in its name.  Moreover, the investigation, carried on by Metropolitan Police officers, was conducted under the direct supervision of the office of the United States Attorney.  Accordingly, in the absence of a contrary interpretation of the Maryland statute by its own courts, we hold that, for the purposes of this case, the surveillance was conducted by a 'federal investigating agency.'  Because we agree that the surveillance