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Jurors on Friday convicted a small-town Iowa letter carrier who admitted sending dud pipe bombs along with threatening letters signed "The Bishop" in an odd but deadly bid to drive up the value of shares he owned.

The jury that heard John Tomkins' case over two weeks spent just two hours deliberating before returning with guilty verdicts on all 12 counts. Tomkins, who had represented himself throughout the trial, looked visibly dejected — hunching forward in his chair, his eyes downcast.

Authorities spent two years trying to track down "The Bishop," eventually identifying him as Tomkins in 2007 with the help of stock market records on the two companies he cited in his letters — 3COM Corp. and Navarre Corp. The 47-year-old Dubuque, Iowa, man admitted sending the packages but insisted they never would explode.

A few minutes after the verdict was read, Tomkins regained his composure, standing to politely ask the federal judge for 90 days to prepare post-trial motions.

"Ninety days is a lot," Judge Robert Dow said skeptically.

"There are a lot of issues," Tomkins responded. Dow gave him 45 days.

Chicago-based U.S. Attorney Patrick Fitzgerald heralded the verdicts.

"The victims who received these threats and bombs were struck with fear, and the agents who conducted this investigation potentially saved lives by apprehending this defendant before he posed any greater public peril," he said.

At times during the trial, Tomkins appeared well-versed in the law, even citing court precedent from memory. But he also sometimes appeared lost. He also frequently referred to himself in the third person, something the judge had instructed him to do to make it clear he wasn't making a personal statement.

"The whole criminal episode has been horrific," he said during his closing. "You do not have to like Mr. Tomkins. He screwed up."

The charges against Tomkins included mailing threatening communications, illegal possession of a destructive device and using a destructive device in connection with a violent crime.

Prosecutors said he sent a dozen letters from 2005 until 2007 threatening to kill recipients, their families or neighbors unless they acted to raise the stock prices. Some letters demanded that the price of 3Com stock be raised to $6.66 by a certain deadline.

In a bid to make them harder to trace, prosecutors said Tomkins drove from Iowa to mail two pipe-bomb packages from the Chicago area in 2007. One was sent to an address in Denver and the other to Kansas City, Mo.

The most serious charge — using a destructive device while mailing a threatening communication — carries a mandatory sentence of at least 30 years. In all, Tomkins could face a more than 200-year term when he is sentenced on Aug. 6.

Tomkins insisted he designed the ominous-looking devices so they could never explode.

Lead prosecutor Patrick Pope rejected that claim, telling jurors Thursday that it was just "dumb luck" that the pipe bombs didn't go off. At one point during the trial, a prosecutor held up cut pipe, a jar of explosive powder and other parts to show jurors the bombs were real.

Tomkins said he got the idea to sign his letters "The Bishop" from a character in Harry Harrison's novel, "A Stainless Steel Rat is Born," where a master criminal left a bishop chess piece as his calling card.

Notes with the packages read, "BANG! YOU'RE DEAD," and stated the only reason the recipient wasn't dead was because a lone wire wasn't attached.

Tomkins, a former machinist, sought to portray himself as a mild-mannered union man fond of building race cars in his garage. Seconds after starting his closing argument Thursday, he stopped, unhinged his clip-on tie and told jurors, "That's not who I am. ... I'm a machinist."

Later, he sheepishly apologized to jurors for his lack of skills as his own attorney.

"Please do not hold my shortcomings against the defendant when it comes to being a lawyer," he said.

After the verdicts, Pope offered some praise for the defendant's performance as de facto lawyer.

"He was courteous throughout the trial, respected of the judge's rules and comported himself very well," Pope told reporters.

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