Paul Callan is a CNN legal analyst, a former New York homicide prosecutor and current counsel at the New York law firm of Edelman & Edelman PC, focusing on wrongful conviction and civil rights cases. Follow him on Twitter @paulcallan. The opinions expressed in this commentary are his own.

(CNN) Paul Manafort could be in big trouble. The cozy house-arrest situation of the former chairman of Donald Trump's election campaign may rapidly change to confinement in a federal correctional facility if a judge in his case believes the special counsel's new allegation of witness tampering.

Judges take a dim view of defendants who improperly pressure witnesses, though prosecutors are rarely chastised and virtually never prosecuted for similar conduct. A tampering allegation could be a devastating blow to the aggressive Manafort defense -- though he has not been charged.

Manafort, who has pleaded not guilty to charges related to his failure to disclose his US lobbying work for a foreign government and to bank fraud and other financial crimes, is currently out on house arrest and a $10 million unsecured bail while he awaits trials in Virginia and Washington, D.C.

Judges view the protection of witnesses as a paramount concern of the criminal justice system and customarily come down hard on defendants who threaten, use improper pressure or clearly seek to suborn perjury.

To date, prosecutors have been particularly tough on Manafort, lodging the most serious charges against him of anyone caught up in special counsel Robert Mueller's investigative dragnet. Many believe federal prosecutors are trying to force Manafort to testify against President Trump.

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