Steven E. Jones is responsible for introducing several new words into the English language. That’s probably the best that can be said about him (at least the current version of him).
Jones is a physicist, and for most of his career, he was known mainly for his work on muon-catalyzed fusion. Then he became a 9/11 troofer (tinfoil hat type) and was relieved of his teaching duties and placed on paid leave from Brigham Young University.
Jones is one of the central authorities of the troofer movement (their main scientific alibi). He believes that the WTC was destroyed by controlled demolition during the September 11 attacks, suggesting that the evidence defies the “mainstream collapse theory” and favors controlled demolition, possibly by the use of thermite or nanothermite. He called for further scientific investigation to test the controlled demolition theory and the release of all relevant data by the government. In other words, he was just JAQing off. He has repeated the claims numerous times, despite the fact that they have been thoroughly debunked (good resource here). His tone subsequently became increasingly accusatory and speculative.
Here’s physicist Dave Rogers on Jones’s original paper; some further debunking can be found here and here.
At least Jones has (thus far) refused to engage with Loose Change people like Dylan Avery, Korey Rowe and Daniel Sunjata, or hologram theorists like Rosalee Grable (various insane claims are documented here), but he is still quite far out.
An awesome (seriously awesome) source for debunking 9/11 troofer claims is here.
Diagnosis: A case study in confirmation bias. Jones is an otherwise intelligent and skilled guy who has been caught up in a typical conspiracy theory mechanism where all evidence that support his view (the truth of which he is already convinced of) is accepted (and thus strengthen his convictions), regardless of whether the pieces defeat each other, and everything that does not fit is dismissed (further strengthening the idea that someone – a conspiracy – is actively trying to deceive him). Very influential in the troofer movement, and must be considered dangerous.