Deputy District Attorney William Hodgman said investigators had insufficient evidence to fill in a timeline stretching over 20 years hampered by the statute of limitations. He did not return a call or email seeking comment Tuesday.
The U.S. Attorney's Office convened a grand jury in 2009 to hear evidence, but it yielded no indictments. It was unclear Tuesday if that grand jury was still sitting and a spokesman declined to comment.
Associated Press writer MaryClaire Dale in Philadelphia contributed to this report.
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