英语听力：自然百科 探索世界奥秘之FBI(揭密联邦调查局)Unit4（在线收听）

Unlike the fertilizer bomb used in Oklahoma City, device analysis reveals that the New Jersey bomb is made from common household items.

The problem is that there are so many things that can be used to make a bomb whether it'd be a digital watch, batteries, or even liquid explosive, they can look like aftershave lotion. By themselves, they look quite innocuous, but assembled together is when they become deadly.

For that reason, the Explosives Unit maintains a huge supply of potential bomb-making ingredients.

We keep an extensive collection of known standard, clocks, batteries, watches, wire, anything that can be used to make a bomb, we try to keep a sample of, so that we can to try to identify using those the piece that we have in.

Using these elements, examiners begin to reconstruct the bomb that killed the New Jersey executive.

We actually lay it all out here in the laboratory and see if we can figure out how it fit together and how it came apart which sometimes will tell us what the type of explosive was used.

So in this, as the bomb is reassembled, examiners realize they are dealing with a serial bomber who's eluded them for years, the infamous Unabomber.

Probably one of the toughest cases that our unit has faced was the Unabomber case. 16 devices, 17 years of investigation, clearly, that was the one that caused us the most trouble.

While serial bombers tend to be meticulous and cleverly illusive, the secret to identifying them is to uncover what the FBI calls the bomber's signature.

The way they wrap wires, the way they tie knots, the materials that they choose to put into the bomb, those things can often indicate to us that we're dealing with someone who's building a series of bombs.

In fact, Sachtleben says the Unabomber literally signed his bombs.

Over several devices, he put the letters “FC” in there to let us know that's who it was. But there was even more of a signature than that. We could tell after looking at the 16 bombs that he had made-------the way that he put his batteries in there, the way that the wires were connected, the soldering that he did. Many of those things indicate to us that it was the same person

Thanks to device analysis and a lucky break, the Unabomber was later identified as this man, Ted Kaczynski. The evidence gathered by the FBI Explosives Unit was instrumental in putting him away for a life. Device analysis is also crucial to solving both the Olympic and abortion clinic bombings. This is a replica of the deadly terrorist bomb that rocked the Olympic Games.

innocuous: harmless, not causing injury or damage; not offensive

elude: avoid; shirk, escape

soldering: act of fusing metal surfaces together with solder