A former Wall Street trader who died suddenly moments after being convicted of arson is being investigated into whether he poisoned himself while in the court room.

Michael Marin was convicted of burning down his $2.55 million mansion in Phoenix after being unable to keep up with mortgage payments.

The 53-year-old faced up to 16 years in jail after being found guilty.

However, once the verdict was read out, he buried his face in his hands and appeared to put something into his mouth, although video is inconclusive.

He took a sip from a water bottle and turned to grab a tissue but his face turned red and he suddenly experienced convulsions and collapsed, pronounced dead at the hospital.

“As you watch the video it does look like he is putting something into his mouth. Unfortunately we didn't find any evidence he left behind," said Jeff Sprong spokesperson for the Maricopa County Sheriff's Office, which is investigating the death.

“We are steering toward the fact he did ingest something. However, we're going to have to wait for toxicology results in two to three weeks.”

Mr Marin made his fortune in finance but the Yale-educated lawyer set fire to his mansion in July, 2009 after being unable to make the $2.3m balloon mortgage payment.

He escaped the fire by climbing down a ladder clad in scuba-diving gear and oxygen tank, with his bizarre escape making officials suspicious.