some initial decisions are overturned on formal reconsideration by the DWP, which leaves a smaller proportion of lingering 'false negatives' to be overturned by independent tribunals. A 2012 study of 28,000 tribunal hearings analysed the reasons for overturning the DWP's decisions: In almost two-thirds of successful appeals, the tribunals found the appellants' descriptions of their difficulties, given in person on the day of the tribunal, sufficiently convincing for them to be awarded the benefit — known as presenting "cogent oral evidence" in legal jargon. By implication, in these cases, the tribunal found the oral evidence more persuasive than had the assessor who had conducted the original face-to-face assessment In nearly a quarter of successful appeals, the tribunals agreed with the DWP on the facts of the case but decided that the DWP had come to the wrong conclusion based on those facts In 13% of cases, documentary evidence was provided that had not been available at the initial assessment In under 1% of cases, the assessment report was found to contain important technical errors. Potential bias In May 2013, a doctor who had recently resigned from Atos blew the whistle on biases in the testing process, telling the BBC: He claimed that: At the face-to-face assessment, the strength of a case was often not weighed as it should have been — on the balance of probabilities — but to a loosely-defined and higher standard of proof, so claimants faced "an uphill struggle" to establish legitimate claims Atos made too little effort, before an assessment, to obtain clinical information that could have a bearing on the case The DWP was "skewing" the WCA in its favour — "pulling strings behind the scenes" by manipulating the training curriculum and the audit protocols it stipulated for the medical assessors who furnished the department with recommendations on claimants' fitness for work The news report drew particular attention to misleading interpretations of the test's eligibility criteria that the doctor claimed were being taught to new assessors as off-the-record rules of thumb during their initial classroom training (and used as benchmarks when assessors' reports were audited). An Atos executive interviewed by the BBC acknowledged that the guidance referred to "might seem somewhat odd" but said it had been "taken out of context" and was part of a much bigger set of questions considered during assessments. On the same day, an Atos spokesperson made it clear that