Hale, who was sentenced Monday to 28 months in prison for mail fraud and conspiracy following a plea agreement, is the key witness for the prosecution.
Tymoshenko, the key political opponent of President Viktor Yanukovich, was sentenced to seven years in prison last October on abuse-of-office charges in a case the West saw as an example of selective justice.
Gilbert said police thought they'd caught a break in 2004 when convicted sex offender Edward Dukette, who served time in a Florida prison for raping and nearly killing a young girl, unexpectedly came forward to police claiming he had key information about Kathy Gloddy's murder.