Three people associated with David Brooks' defense provided writing samples and were fingerprinted Wednesday under the supervision of FBI agents investigating whether the former body-armor magnate had tampered with the jury considering his fraud case.

The three were Brooks' brother, Jeffrey Brooks, and two paralegals -- Aaron Hendel and Jil Klinkert, who is also David Brooks' girlfriend.

The FBI agents at the federal courthouse in Central Islip were acting for a grand jury looking into a note that federal marshals say Brooks had attempted to conceal. The note was among a pile of legal documents given to David Brooks Monday by Hendel.

Jeffrey Brooks, Klinkert and Hendel did not testify before the grand jury, which is still apparently gathering material for its probe. The three declined to comment, as did Jeffrey Brooks' lawyer, Steve Sparling; Klinkert's lawyer, Judd Burstein, and Hendel's lawyer, Deborah Colson.

Robert Nardoza, a spokesman for the U.S. Attorney for the Eastern District, whose prosecutors are heading the investigation, declined to comment.

The grand jury investigation began when U.S. District Judge Joanna Seybert said the note might indicate that Brooks could have been tampering with the jury. She added that the note might have other more innocuous meanings.

A federal marshal said she had noticed Brooks tear the handwritten note from a typed legal document and attempted to conceal it. Brooks' lead defense attorney, Kenneth Ravenell, originally said the note was a valid legal document, although he acknowledged he did not know who wrote it.

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Now sources are saying Brooks is alleging that the note involves horse racing matters.

Brooks was the owner of the largest stable of trotting horses in North America, but he has said he gave up his interest to his brother Jeffrey and other family members after he was charged with looting his former Westbury company, DHB Industries, to pay for a luxurious lifestyle and illegally making $185 million in a stock scheme.

Several racing bodies in Canada and the United States have been considering to what extent David Brooks still controls the family harness interests.

The flap over the notes is not the first time that Klinkert and Jeffrey Brooks have been involved in controversy at the fraud trial. Seybert previously barred the two from entering the courtroom after David Brooks was found to have concealed tranquilizer pills in pens that were placed in an area where the two had brought in papers and writing materials.