By September, 14 other police stations in south London will join the scheme
A pilot scheme assuring "swift justice" by allowing defendants to be dealt with via a secure video link from a police station has begun in London.
Under the "virtual courts" scheme, defendants make their first appearance from a room at a police station equipped with a camera.
The scheme aims to cut delays caused by missing paperwork and defendants failing to turn up.
But The Law Society said it could compromise solicitors' safety.
The current pilot links Charing Cross Police Station with Camberwell Green Magistrates' Court, in south London.
A further 14 police stations in London will join the pilot over the summer.
It has already seen one defendant jailed without ever entering a court building.
The man, who admitted drink driving, was also fined and banned from driving last week only hours after he was arrested.
"Virtual courts have the potential to transform how the justice system deals with crimes," said Justice Secretary Jack Straw.
"They are vital in the government's drive to deliver swift justice - resolving cases faster, freeing up police time and improving the service given to victims, witnesses and defendants."
Defendants pleading guilty may be sentenced on the spot but there are no plans to extend the scheme to include full trials, Mr Straw said.
But the Law Society expressed serious doubts over the plans.
"The society has grave concerns over the safety of its members," said a Law Society spokesman.
"Under this scheme defendants will be sat in a small room right next to their solicitor - Jack Straw avoids the fact that in a conventional court, the client will be in a dock with dock officers."
If successful, the pilot could lead to £2.2m in savings over the year across the criminal justice system.
A second pilot in Kent will begin next month. A wider roll-out of virtual courts in other areas across England and Wales could deliver savings in excess of £10m a year, the government claims.
Youths, people with mental illnesses and any cases involving more than one defendant are excluded from the scheme.
More defendants could be tried in virtual courts as 14 more police stations join the scheme over the summer