Lawyer Joel Garcia, who has defended opposition figures in Venezuela, said if Mr Gonzalez Urrutia was charged with everything the government has accused him of, he could face a jail sentence of 30 years.
Prior to the election, Mr Gonzalez Urrutia was a little-known retired diplomat.
He became the last-minute presidential candidate after the main opposition figure was banned from running by state institutions seen as loyal to Mr Maduro.
After Venezuela’s last election, in 2018, Mr Maduro was proclaimed winner amid widespread accusations of fraud.
He has led the oil-rich but cash-poor country since 2013.
His tenure, which has suffered from domestic economic mismanagement as well as international sanctions, has seen GDP drop 80 per cent and more than seven million of the country’s 30 million citizens emigrate.