A Philadelphia man and woman were charged Thursday with offering a bribe to prevent a witness from testifying before a federal grand-jury investigating the illegal possession of a firearm.

As authorities tell it, Troy Cooper, 42, and Tiffany Reid, 24, thought $500 would be enough to scare off the witness.

The indictment said that Cooper and Reid initially tried to get the witness to avoid complying with a federal grand-jury subpoena on Sept. 16, 2011, but apparently weren't successful.

Nine days later, Cooper and Reid offered the witness a $500 bribe to prevent their testimony before the grand jury, the indictment said.

Cooper and Reid, who were both charged with witness-tampering and related offenses, had initial appearances before a federal magistrate Thursday.

Reid was released on bail with conditions; Cooper was detained pending a May 15 bail hearing. n

Contact Michael Hinkelman at 215-854-2656 or hinkelm@phillynews.com or follow on Twitter @MHinkelman.