She was notorious for maintaining information on prominent citizens (and even her fellow Judges). She sometimes used this information to maintain her position and to play power games within the department.
Edgar became joined PSU when she lost the use of her legs after receiving a back injury when wounded in the line of duty. An ambitious Judge, in the 2090s Edgar was part of a small group of judges that committed vigilante murders under the alias of the Citizens' Court. Thanks to her job at the PSU, Edgar was able to ensure that the others were not caught. After seventeen killings, she had the group disbanded so it could not cause problems for her career advancement. The other Court members would also go on to high rank, with Judge Hoolio Ramos joining the Council of Five.
In 2100, she became the head of PSU. She became renowned for her strict discipline and high expectations of her staff. Occasionally, she used the wealth of confidential information at her disposal to play power games with other judges to increase her own influence. Even the Special Judicial Squad would avoid clashing with her.
In 2117 she was discovered to be illicitly keeping sensitive information on other senior judges, which had been compiled by Judge Cal for the purposes of blackmail when he was head of the SJS. This information covered Chief Judge Hadrian Volt himself and even Eustace Fargo. This came to light when it was stolen and she sent Dredd to retrieve it - and manipulated him into investigating copying the data and investigating the allegations on Fargo. Edgar had long wanted to know if Fargo really had been in an affair with Arden Polders and felt Dredd was the best man to investigate, but would rather trick him into it than ask outright. In the end, Dredd turned the copy (after Edgar had destroyed the original) over to Chief Judge Volt and passed on the information about Polders to Edgar. The affair also revealed a large amount of Cal's files did not have legitimate evidence: Fargo hadn't been seeing a mistress, he'd been filmed visiting his sister.
Volt decided against taking action against Edgar.
To avenge herself on Judge Dredd for a perceived slight against her, she orchestrated a disciplinary investigation into Judge DeMarco – one of Dredd's associates – in order to dig up dirt that she could use on him. When the SJS learned DeMarco had kissed Dredd and he hadn't reported it, Edgar 'adviced' SJS Judge Muncie to not pursue Dredd for breaking regs so they wouldn't "appear too... vindictive". Instead, the full weight would be brought down on DeMarco – which led to DeMarco's resignation – as a way to punish him with 'clean hands'. She made sure that Dredd would learn she'd been behind DeMarco's fall. 
When Nero Narcos built up to the Second Robot War, PSU were completely unaware until the robots attacked. Their headquarters were stormed and Edgar was taken hostage, taunted by Narcos at how easy it had been. When the tide began to turn, she quietly informed him that Justice Department was a machine that wouldn't stop running just because of a few faults. Narcos' last order was for Edgar to be shot. His robo-butler instead took her to the Judges as it wanted to avoid being scrapped.
When Hershey became Chief Judge in 2122, she immediately had Edgar arrested and investigated by the SJS for her use of the Cal Files. On trial before the Council of Five (with Dredd temporarily on it), Edgar defended herself with skill and defiance. She briskly and brusquely discredited what had initially seemed to be overwhelming evidence, reducing the prosecution case to nothing more than empty innuendo, and claiming that the charge was politically motivated.
Although Edgar was acquitted of all criminal charges, she was still dismissed from office by Chief Judge Hershey. Judge Niles, who was head of SJS and who had personally led the investigation (and brought the whole affair to Hershey's attention in the first place), was transferred from SJS to take over command of the PSU. Edgar was demoted to the lowly position of commanding Cursed Earth Correctional Facility 17, where she remained for eight years.
As warden, she allowed prisoners to try scaling the cliff walls. Everyone who tried would fall and die, which she wrote off as "their choice" and would bitterly remark to Dredd that it was better than "rot[ting] your days away in Correction Facility 17". When Armon Gill, an assassin used by someone within Justice Department, killed a prisoner with a similar record to his own, she suspected that this was a deliberate act to cover up his employer's tracks. In an act of spite, she didn't report it. 
Dredd would visit her in 2125 when trying to uncover the Judge running the assassin Gill: he felt she had the sharpest mind on the force and he wasn't proud enough to not ask her. While resenting the fact he was asking her for help, the puzzle had her interested and she gave him her thoughts. Afterwards, tired and lonely, she ended up asking him for news from home. 
By 2130 she was in very ill health and on the verge of death from cancer. In one final scheme for revenge, she steered Dredd towards the remaining members of the Citizens Court in the hope that Dredd would be killed by one of them resisting arrest. By the time Dredd had uncovered her involvement she had died, too late for him to arrest her for the murders.