His widow Marina rejected allegations that he had bought the radioactive substance polonium-210, saying he was a "very legal person".
She also told the court Mr Litvinenko had been warned he would be killed on different occasions.
Mr Litvinenko was a vocal critic of the Russian government and spy agency FSB.
The inquiry also heard from his son Anatoly, 20, on Tuesday. He said he felt "numb" after his father's death.
Mr Litvinenko, who fled to the UK in 2000 and had British citizenship, died nearly three weeks after drinking tea laced with polonium at a hotel in London in November 2006.
Two men - former KGB bodyguard turned politician Andrei Lugovoi and Dmitri Kovtun - were named as the main suspects in 2007. Both deny any involvement and remain in Russia.
The judge-led inquiry at London's Royal Courts of Justice was shown a video of Russian soldiers using an image of Mr Litvinenko as target practice.