2 possible reasons the pipe bombs didn’t explode

The 13 pipe bombs sent to former President Barack Obama, former Secretary of State Hillary Clinton, and 11 others didn’t explode — and there are two plausible explanations for why.

The first is that there are best practices to identify when someone has sent explosives through the mail, like when names are misspelled. In this case, a postal worker found one of the the pipe bombs at a post office and alerted authorities.

What’s more, many public figures who may be potential targets of attacks have mail-screening areas in their employ, staffed with experts who know how to identify suspicious packages. Put together, these measures lower the chances that the dangerous mail ever reaches the potential victim.

FBI via Getty Images

The second possible reason is that the bombs couldn’t detonate because the wires didn’t connect to a trigger, meaning they wouldn’t have exploded even if they’d reached their intended target. Anthony May, a retired government explosives investigator, told Vox that based on X-rays of the pipe bombs leaked online, he believes the devices were “not capable of functioning.”

In a Friday press conference, FBI Director Christopher Wray said “these were not hoax devices,” indicating the bomber tried but failed to make the explosives work.

The suspect is now in custody and has been charged with five federal crimes, including trying to kill a former president, which if convicted would place him in jail up to 48 years. But Wray added that other packages may yet be in transit, which means there’s a chance a working bomb remains undiscovered.

Let’s take each reason in turn.

Experts know how to identify suspicious packages

Jimmie Oxley, an explosives expert at the University of Rhode Island, told Vox that the packages that contained the bombs featured several of the telltale signs experts look for when screening for potentially dangerous mail.

“You look at this package that’s got six stamps on it — when we teach looking for suspicious packages, too much postage is the No. 1 thing we say,” Oxley said, adding that several of the manila folders containing the bombs also had misspelled names and too much tape.

Those three things typically indicate troubling mail, but law enforcement has also identified other clues:

• No return address on the package
• Markings that indicate the materials can only be seen by a specific person
• An envelope that shows signs of unknown substances, like odorless powders

The FBI tweeted out a handy infographic with all this information on October 25:

Many celebrities, prominent public figures, and current and former top government officials use mail security services to screen their packages before they reach the intended recipient, Oxley said. Those services know how to spot a dangerous package before it hurts anyone and whom to call to safely remove a possible explosive.

Workers at the US Postal Service, like the one who found a pipe bomb on Friday, also know how to identify troublesome mail.

So at least part of the answer as to why no one was hurt by these pipe bombs, it seems, is that mail security is fairly tight.

The bombs weren’t well made

May, the explosives expert who has investigated serial bombings for decades, thinks that the bombs were poorly made and thus unable to detonate.

Though he’s not involved in the investigation and hasn’t actually seen the devices himself, May said that, based on his independent analysis of released X-rays of the bombs, they included features that would have rendered them inert — including wires inside that didn’t seem to lead to a switch to set them off.

But much of the bomb included the right materials to make a successful explosive, May told Vox. According to the federal charges against the suspect, each bomb “consisted of approximately six inches of PVC pipe, a small clock, a battery, wiring, and energetic material.”

It’s unclear if the bombing suspect failed to make bombs work from the start, or if they somehow came undone in the mail.

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