Judge Sinfield was the head of Traffic Division until 2120, when he was transferred to take charge of re-organising Administration. In 2131, when Chief Judge Hershey's controversial policy of granting citizenship to mutants resulted in a dramatic fall in her popularity, Sinfield was one of three senior judges (with Cardew and Millan) who led a campaign to remove her from office in a recall election. When this triumvirate's chosen candidate, Judge Dan Francisco, was seriously injured in an assassination attempt, Francisco easily won the election and became chief judge. Sinfield's reward was promotion to deputy chief judge, and consequently he served as acting chief judge while Francisco remained in hospital, recovering from his wounds. From this position, Sinfield easily established himself as the real power behind the throne.
One of their first acts was to exile Judges Dredd and Hershey from the city for their role in promoting mutant rights. Dredd was sent to the Cursed Earth to oversee the construction of four new mutant townships which were being set up in the Cursed Earth to house the recently deported mutants.
Like many judges, Sinfield has been cloned. When Sinfield's clone, Judge March, was given his Final Assessment, Judge Rico found him wanting and failed him, incurring Sinfield's ire. In revenge, Sinfield exiled Rico to the Cursed Earth townships as well. Due to Sinfield's mediocrity, Dredd and Rico suspected that he had corruptly sneaked his DNA onto the cloning program. However their efforts to prove this met a dead end.
Even once Chief Judge Francisco was well enough to run his own administration, Sinfield manipulated him to some degree, for example by using his influence to exile Rico. Nevertheless, Sinfield did not always get his own way. He clashed with Francisco when the Chief Judge overruled his objections to spending more money on the mutant townships.
Francisco was aware that his deputy was trying to manipulate him, but he still did not dismiss him as he believed Sinfield had the city's best interests at heart. However, Francisco's confidence was badly misplaced. Sinfield was a stern hardliner on the mutant issue, and eventually he became disillusioned with Francisco's relatively compassionate treatment of mutants, and with his willingness to spend what Sinfield regarded as extravagant sums of the city's strained budget on ensuring the mutant townships were somewhat decent places to live in. Finally resorting to criminal means, Sinfield used a powerful hypnotic drug to subvert Francisco's will, and then encouraged him to resign. With Francisco's resignation in 2132, Sinfield automatically became acting chief judge, and at once set about imposing harsh anti-mutant policies, such as automatic deportation for the most trivial of offences.
On Sinfield's first day in office, Judge Dredd lodged a formal complaint against him with the Council of Five, accusing Sinfield of gross negligence in failing to provide him with sufficient resources, almost leading to the death of one of the judges under Dredd's command, Judge Munn. However, Dredd's hopes of receiving even a partially sympathetic hearing before the Council were soon dashed when Sinfield simply replaced the more moderate Council members with hardliners like himself.
Sinfield also incurred the displeasure of the Mayor of Mega-City One, Byron Ambrose, when he attempted to bully him into changing his policies to raise more revenue. Unaware that Mayor Ambrose was in fact the infamous serial killer PJ Maybe, who had stolen Ambrose's identity, Sinfield threatened to undermine his re-election campaign. Maybe retaliated by covertly infecting him with a deadly fungus. However he survived not only the fungus but also Maybe's next attempt, using another deadly disease. Consequently Sinfield recalled Judge Dredd from the Cursed Earth to investigate the attempts on his life, believing Dredd to be the best man for the job. Dredd uncovered Maybe's involvement after he personally thwarted a third murder attempt.
Unfortunately for Sinfield, during the investigation Dredd's aide, Judge Logan, uncovered the fact that Sinfield had accessed an archived evidence file holding old evidence relating to PJ Maybe, leading Dredd to begin to wonder just why Sinfield had wanted it. It was actually from this file that Sinfield had obtained the hypnotic drug which he used on Francisco. However Sinfield refused to explain himself to Dredd, and so his crime was not immediately discovered.
Nevertheless, Dredd was so disgusted with Sinfield's dereliction of duty in endangering the life of Judge Munn, and the subsequent whitewashing of the affair by the Council of Five, that he decided to run against Sinfield in another recall election. During the election campaign, Dredd finally uncovered Sinfield's theft of the hypnotic drug, and arranged for him to be arrested. Sinfield was removed from office, convicted by the Council of Five, and sentenced to 20 years' hard labour on a penal colony on Titan. The truth was initially witheld from the public, who were told he had resigned due to ill health. However Chief Judge Francisco, on returning to office, decided that it would not matter if Sinfield's real fate was leaked: it would send a message to the citizens. Once arriving on Titan, Sinfield became the centre of attention, with many of the inmates loathing him (several had been sent there because of him).
Sinfield's fate was soon officially acknowledged, and he was not expected to survive his sentence
He's shown to be a selfish, power hungry and rascist jerk who allowed the anti-mutant sentiment in Mega-City One to flourish and caused the city's economy to stagnate. He's also skilled at manipulating which made Judge Francisco think that even though he knows Sienfield's manipulating him, he has the city's best intrest at heart even though that's clearly not the case. He also tends to bully people into getting his own way such as him trying to bully Byron Ambrose (PJ Maybe stole his identity) change his policies on the revenue.