A former member of the Red Army Faction, Verena Becker is on trial in Germany accused of involvement in an assassination in 1977.
Siegfried Buback was senior prosecutor in what was then West Germany when he was killed in an ambush.
The Buback case was reopened two years ago when new DNA evidence linked Ms Becker to the killing.
The Red Army Faction carried out a series of high-profile killings and kidnappings in West Germany in the 1970's and 80's.
Also known as the Baader-Meinhof gang, the group killed more than 30 people. before they broke up more than 10 years ago.
Ms Becker, 58, was arrested last year for her suspected role in the ambush of Mr Buback. Two men escorting him were also shot dead when their car stopped at traffic lights on the way to a court in Karlsruhe.
Police say there is DNA evidence implicating Ms Becker on a letter in which the RAF claimed responsibility.
Although Ms Becker was arrested the month after his assassination, after a shoot-out with police, the BBC reports there was insufficient evidence at the time to convict her of his murder.
She was sentenced to life imprisonment for her involvement in six other murders, but was pardoned by then-President Richard von Weizsaecker in 1989 and released.
She was rearrested in August 2009 and charged earlier this year with conspiracy to murder after new forensic technology reportedly revealed traces of Ms Becker's DNA on a letter by the RAF sent claiming responsibility for the Buback attack.
The BBC reports the trial is expected to continue until December. Ms Becker faces a possible life sentence if convicted.
