Internet shock jock and F.B.I. confidential informant Hal Turner beat the rap again when his second federal “Death-Threat Trial,” ended in yet another mistrial.

Turner, charged with threatening the life of three federal judges who issued rulings supporting gun control, claims federal agents encouraged his seemingly dangerous rants over the years, and told him to “ratchet up the rhetoric” while asking for help in identifying a white supremacist killer. Government officials admit using him as an informant (beginning in 2004 and culminating in 2007) for intelligence on members of white supremacist groups, among whom he had a devoted following. Turner’s background as a paid F.B.I. informant has now become the main issue in the thus far unsuccessful prosecution.

As the New York Times reported, “Before, during and after his employ as an informant — sometimes to the chagrin of his handlers and sometimes at their request — Mr. Turner continued to use his radio show and Web site to spout racist and, at times, violent rhetoric aimed at elected officials, public personalities and judges.”

Suddenly last summer, however, Turner was arrested, accused of posting photos of the judges and saying they were “worthy of death.”

In his hours on the witness stand, Turner detailed his ascent as a shock jock, as well as his relationship with the F.B.I.. Michael A. Orozco, one of Turner’s lawyers, offered as a defense that his client is “nothing but a shock jock.” Turner’s “hand was guided by the Federal Bureau of Investigation,” Orozco said. “He was providing a service. This is betrayal.”

Turner has long been notorious for making anti-immigrant, anti-Semitic, white supremacist remarks and encouraging violence on his Internet radio show and companion Web site.

Last June, for example, he posted this message: “The government — especially these three judges — are cunning, ruthless, untrustworthy, disloyal, unpatriotic, deceitful scum.” The judges all testified at trial that they felt threatened. Turner later took the stand to say his rants were an F.B.I.-sanctioned ruse to ‘’flush out'’ dangerous members of his audience.

Were Turner’s comments a clear threat, as prosecutors alleged, or simply “the type of free speech that the F.B.I. had encouraged and condoned in the past,” as defense lawyers contended? Despite the fact that the government actually brought in the judges who were Turner’s targets to testify in the second trial, two sets of jurors have now failed to come to a consensus on that crucial question.

A new trial date has been set for April 12, and lead prosecutor William Hogan, says “it’s highly likely” the government will take another bite at the apple. Third times a charm?

Turner also faces state charges in Connecticut, for telling his followers to “take up arms” against state lawmakers who voted to give Catholic lay members more control over church finances.