Murder of 'essential' witness was arranged from behind bars, court told

A Sydney man who was facing drug charges plotted the murder of an "essential" witness in the case against him from behind bars, a court has heard.

Luke John Sparos has pleaded not guilty to murdering Gemahl Maika, 38, by arranging for another man to shoot him for payment at the home of Mr Maika's family in Glen Alpine in April 2011.

In his opening address at Sparos' NSW Supreme Court trial on Monday, prosecutor Craig Patrick SC said the 37-year-old was "ultimately responsible" for the killing and equally as liable for it as the man who shot Mr Maika five times.

"Mr Sparos instigated and organised the killing of Mr Maika, using other people," Mr Patrick said.

Sparos had begun plotting the murder while awaiting a trial, both as "retribution" against Mr Maika for his evidence and to send a message, he told the court.