Wolfgang Plan, 50, was convicted by the regional court in the southern city of Nuremberg of murder in a case that sparked a nationwide crackdown on radical right-wing groups.
Plan, who referred to himself exclusively in the third person during the trial, smiled as he entered the courtroom wearing a dark suit. He sat impassively as the presiding judge read out the verdict.
He had denied intending to kill the 32-year-old officer during the trial, which started in August, as well as membership of the so-called Reichsbürger (Citizens of the Reich).
The group includes neo-Nazis, conspiracy theorists and gun enthusiasts who reject the legitimacy of the modern German republic.
Plan told the court through his lawyer that he thought he was under attack when his house was stormed in the “amateurish” raid in October 2016, and had no idea he was firing at police.
One policeman was critically injured and later died of his wounds, while two others were injured in the confrontation in the town of Georgensgmuend.
As a result, Plan was also convicted on two counts of attempted murder. His defence attorneys had called for a verdict of manslaughter, with a significantly milder prison sentence.
Prosecutors argued Plan, a hunter who once ran a martial arts school, fired 11 shots “with the intention of causing as many deadly injuries as possible”.
The raid was aimed at seizing Plan's arsenal of about 30 weapons after his permits were rescinded following an assessment that he was psychologically “unsound”.
He had previously refused to pay taxes and handed in his official identity card.
'My word is law'
Reichsbürger followers generally believe in the continued existence of the pre-war German Reich or empire as it stood under the Nazis, and several groups have declared their own states.
They typically deny the legitimacy of police and other state institutions and refuse to pay taxes.
News agency DPA said Plan had established a pseudo-state on his property, drawing “borders” around it with yellow lines and hanging a sign reading “My word is law here”.
Bavaria state interior minister Joachim Herrmann said the court had handed down a “tough sentence that is appropriate for the brutality of the crime”.
Long dismissed as malcontents and oddballs, the Reichsbürger are seen as a growing threat after a string of violent incidents.
Since Plan's arrest, police have carried out a series of raids against suspected Reichbürger militants, seizing arms and making several arrests.
Security services believe some 15,000 people in Germany identify as Reichsbürger, some 900 of whom are known far-right extremists.
Two months before the deadly shooting in Bavaria, a then 41-year-old Reichsbürger and one-time “Mister Germany” pageant winner, Adrian Ursache, opened fire on police carrying out an eviction order at his house in the eastern state of Saxony-Anhalt.
The gunman was seriously wounded and three officers suffered light injuries.
After repeatedly disturbing the proceedings before the court in the city of Halle, he was barred from the courtroom last week. His trial will continue in his absence.