A leading NASA scientist pleaded not guilty Thursday to charges that he tried to sell US defense secrets to Israel.The Judge rejected a bail request from Stewart David Nozette, saying he was considered a flight risk.

Court documents from the prosecution accused Nozette of selling classified information to an individual he believed was an Israeli intelligence officer.

In exchange, Nozette received an alias, a foreign passport, and cash payments of two million dollars.

In their final discussion, the undercover FBI agent allegedly handed Nozette 10,000 dollars in 100 dollar bills.

Nozette tried to hide the bills inside a hotel bathroom toilet tank when federal agents arrested him. The FBI also searched Nozette’s safe deposit box, where they discovered 55 South African gold coins.

The prosecution argued that this meant Nozette would flee if given the chance, and should therefore be refused bail.

Nozette worked at the US space agency NASA, , and even served on the White House National Space Council, under then-president George Bush Senior. He had security clearance for many years. If convicted, Nozette could face the death penalty although his execution is considered unlikely.

The only US civilians ever executed for espionage were Soviet nuclear spies Julius and Ethel Rosenberg back in 1953.