In 2012, she reported on the inquest at South Central Coroners Court regarding the shooting of Karim Ali by members of the Strategic Firearms Command in a Counter Terrorism operation. Despite the official statement released by Chief Inspector Philip Osborne, Vella questions its authenticity and appears to side with the account of Aaliyah Ali that the shooting was unjustified.
Her news team reported on the trial and sentencing of former Chief Superintendent Patrick Fairbank, who was found guilty at the end of Series 3 for his involvement in the sexual abuse at Sands View as well as covering it up.
Vella was also retrospectively established as present at the press conference held by PCC Rohan Sindwhani and DCC Andrea Wise outside Pelbury House at the end of Series 5, in which they (falsely) announced that Operation Pear Tree had not uncovered institutional corruption within the police force.
For her investigative efforts she was awarded a journalists commendation, and was featured on the front cover of Impact Magazine.
Vella is already dead at the start of the series, with DCI Joanne Davidson and her team out of Hillside Lane Station having been assigned to investigate her murder. Davidson's approach to investigating the case draws the attention of Anti Corruption Unit 12.
It is revealed that Gail was shot dead after exiting her car, with evidence suggesting she was shot with the gun pressed against her head to reduce excessive sound and debris from the gunshot. Terry Boyle is taken into custody by DCI Davidson as a suspect for her murder, with an investigation of his property revealing he had several photos of Vella taped to his wall. Forensic evidence also revealed traces of Boyle's semen on the photos, implying Boyle wanted to have a sexual relationship with Vella with Davidson alleging that he murdered her because he was angered that he couldn't be with her. However, no forensic evidence relating to Vella's blood or tissue was found at the crime scene meaning Davidson couldn't charge Boyle with her murder, much to the chagrin of Superintendent Ian Buckells.
When Anti Corruption Unit 12 detectives DI Steve Arnott and DC Chloe Bishop interview her former producer at MN News, Haran Nadaraja, he reveals that as a female journalist she was subjected to "the worst of it" when it came to threats and criticism, and received many threats of sexual abuse. He also shows them a report made by Vella that was controversial and had to be edited before broadcast. In it she is seen reporting on the press conference held by PCC Rohan Sindhwani and DCC Andrea Wise outside Pelbury House after the closure of Operation Pear Tree, in which she accuses them of telling "attractive lies" in response to their claims the investigation revealed no institutional corruption in Central Police.
It is revealed that because Vella could not get certain more controversial reports broadcast on MN News, she had been in the process of starting her own podcast that would detail her investigations into the links between Central Police and Organised Crime Group, as well as police coverups of scandals involving political figures like Councillor Dale Roach. She had been inspired to start the podcast by seeing the success of another, which explored links between corrupt police officers and the death of a private investigator named Daniel Morgan. Nadaraja tells the detectives she had contacted several senior police officers to interview before her death, and had kept numerous notes and recordings.
However, he then tells Arnott and Bishop that when he was first interviewed by the Murder Investigation Team after Vella's death, they told him no notes or recordings were found in her flat or office. When he suggested they might have been stolen by whoever killed her, this was dismissed by the detectives as apparently there were "no signs of a burglary".
After searching through the system, Haran Nadaraja uncovers other footage filmed by Vella on behalf of MN News which could be considered "controversial", and forwards them to AC-12. The two new clips include one of Vella confronting Chief Constable Philip Osborne outside of Pelbury House about inaccurate statements he had made regarding the number of new officers recruited into Central Police. The other is an unaired interview with PCC Rohan Sindwhani, who storms out after she begins asking him questions about police coverups into child sex offenses, such as the case with former Chief Superintendent Patrick Fairbank and Councillor Dale Roach.
Specialist Technician Amanda Yao uncovers another audio recording from a hard drive belonging to Vella, taken from a computer used by her at the MN News offices. The recording is of a conversation with an unknown man discussing police corruption specifically linked to Chief Constable Philip Osborne; he also mentions racism in the force and former DCI Roz Huntley, which makes DI Arnott think of Operation Trapdoor. Upon hearing the man speak about Balaclava Man, Arnott realises the man in the recording is former lawyer Jimmy Lakewell, imprisoned at HMP Blackthorn. When confronted by Arnott and DC Chloe Bishop in the prison visiting room, he admits speaking to Vella but declines to answer any further questions, alluding such matters are not safe to be discussed in the presence of a SecuritVite security officer. He is transported out of prison in an armed convoy by AC-12 and offered witness protection in exchange for information on Vella's investigation and how they could link to her death. Arnott hypothesises he was "testing the waters" by speaking with Vella, as revealing such information could lead to him being put in witness protection. After an OCG ambush on the convoy that results in the death of PS Ruby Jones, he withdraws his cooperation and returns to Blackthorn where he is murdered by Lee Banks.
DI Steve Arnott reveals that during the convoy ambush Lakewell did actually speak to him, and told him that a significant case of police corruption Vella was looking into was the murder and death in custody of Lawrence Christopher in 2003. Christopher died in a custody cell after being beaten in a racially motivated attack, but responding officers with the Patrol Unit refused to offer him medical treatment and subjected him to racist taunts as he died from his injuries. Vella was exploring the possibility that Organised Crime Group leader Tommy Hunter was able to use his influence with corrupt police officers at the time to get the SIO in the Lawrence investigation, DCI Marcus Thurwell, to sabotage and delay the arrest of the perpetrators in order to protect his son, Darren Hunter, who was one of the attackers. Through further research by DC Chloe Bishop, it is revealed that DSU Ian Buckells (then a DC) and Chief Constable Philip Osborne (then an Inspector) worked alongside Thurwell and could have been involved in the coverup, thus rendering them both beneficiaries of her murder.
It is also revealed that as part of her wider investigations into the links between the Organised Crime Group and Central Police, she had made requests with the UK Prison Service to interview numerous individuals currently imprisoned as a result of AC-12 investigations. This included former DS Manish Prasad, former PC Hari Bains and former CSU Patrick Fairbank at HMP Blackthorn, as well as former DCI Roz Huntley, former PS Jane Cafferty and former PS Martina Tranter at HMP Brentiss. She even made contact with Witness Protection to seek authorisation to interview both Lisa McQueen and Gill Biggeloe. However, none of the former officers agreed to speak with her. The only person who agreed to be interviewed was Lee Banks, a member of the Organised Crime Group who worked under rogue DS John Corbett. They spoke on the 25th August 2019, only two weeks before she was murdered. Arnott theorises Banks only agreed to speak with her to discover what she knew, and then passed the information on to his brother Carl Banks who was then instructed to silence her by more senior members of the group.
In an effort to prove to DI Kate Fleming that she is not fully corrupt, DSU Joanne Davidson leads AC-12 to the abandoned Kingsgate Printing Services building before she is arrested. The building, located opposite Dorton Villas (the residence of Terry Boyle), had been abandoned for 18 months since the death of DS John Corbett, the death of Miroslav Minkowicz and defection of Lisa McQueen. Upon searching it the detectives discover a hidden metal strongbox, which contains laptop and desktop computer that was stolen from Vella's house the night she was murdered and replaced with decoys. Davidson insists she did not place the items there, but found them on a hunch given the buildings location. She further states her presumption that the Organised Crime Group would use the abandoned building as a hiding place as it had previously been searched thoroughly by the Forensic Unit as part of Operation Pear Tree 18 months prior, and no police officers would think to re-search it. The Cyber Crime Unit determines the OCG accessed the computers using Vella's passwords, with DI Steve Arnott hypothesising they were obtained by threatening someone in the IT Department at MN News.
After drilling through the concrete flooring of the Organised Crime Group's workshop in the White Rock Industrial Park, officers uncover a strongbox containing various pieces of evidence kept by the group as leverage against its other members. A modified Beretta pistol matching the type used to kill Vella, as well as a bomber jacket and gloves containing the DNA of Carl Banks and Vella's blood are among the items, definitively confirming he was the one who murdered her.
After The Fourth Man is revealed to be DSU Ian Buckells, he insists he simply passed information on to the OCG and was never organised in the planning or execution of their crimes. Detectives from AC-12 acknowledge that the OCG would have motive to murder Marcus Thurwell and Jimmy Lakewell, as they were directly linked with the group and their loyalty was in question after the death of Tommy Hunter. However, DI Steve Arnott and DI Kate Fleming note that the OCG on its own would have no reason or benefit to decide to murder Vella themselves, especially in such a high profile manner that would draw attention. Although she had spoken with Lee Banks about the groups connection to the sabotage of the Lawrence Christopher case in 2003, the only person vaguely connected to the group and the Christopher murder was Darren Hunter. Hunter was a "nobody", especially since the death of his father Tommy Hunter, was likely unaware of his fathers involvement in sabotaging proceedings against him in 2003, and had never become involved as a useful member of the OCG anyway. Therefore, murdering Vella would not have been worth it, as the group had no reason or motivation to protect Hunter from being arrested.
Superintendent Ted Hastings instead proposes that she was murdered specifically on the order of corrupt officers linked to the group, as both Buckells and Chief Constable Philip Osborne would have far more to lose by being connected to the Organised Crime Group through Thurwell and the botched Lawrence Christopher investigation than members of the OCG. It is strongly suggested that it was Buckell's himself who used his influence to persuade Carl Banks to murder Vella so she could not reveal her findings that could implicate him and Osborne as being long involved with organised crime.