Cape Town - The decision by former National Prosecuting Authority head Mokotedi Mpshe not to prosecute President Jacob Zuma on 783 charges of corruption was "clouded by emotion, unsubstantiated facts, an inadequate investigation", the Democratic Alliance submits in court papers.Zuma and the NPA are asking the Supreme Court of Appeal (SCA) to grant the leave to appeal the North Gauteng High Court's April 2016 ruling that the corruption charges must be reinstated. The DA, who fought a long court battle on the matter, is a respondent, and chairperson of the DA's federal executive James Selfe filed their papers with the SCA on Monday.The DA asks that leave to appeal be dismissed with costs.The North Gauteng High Court's full bench ruled in April 2016 that the decision to discontinue the prosecution against the president should be reviewed and set aside. The court ruled that Mpshe's decision to drop the charges in 2009 was irrational.Appeal In its affidavit, the DA contends that the court's findings on procedural irrationality "are critical and fatal to the applications for leave to appeal". "Even if the NPA were to be successful in convincing this court on all other aspects, the impugned decision would still be procedurally irrational, and invalid," the DA submits."In the circumstances, it is submitted that Adv Mpshe’s decision was clouded by emotion, unsubstantiated facts, an inadequate investigation, confusion about his own role, and confusion about the effect of Mr McCarthy’s actions," reads the submission. McCarthy refers to former Scorpions boss Leonard McCarthy, who was recorded discussing Zuma's prosecution with former NPA boss Bulelani Ngcuka. Mpshe based his decision on the premise that this recording showed political interference in the decision to charge Zuma.According to the DA, "this is the very antithesis of a rational decision". "Based on the material before him, he could not rationally have reached the decision he did that this case involved an abuse of the kind which was so serious and so egregious, that it justified the extraordinary step of withdrawing the prosecution of Mr Zuma."According to the DA, Zuma’s application for leave to appeal suggests that the rationality of Mpshe’s decision cannot be tested against his stated reasons alone, but should be viewed "in context". "By this, it appears to be suggested that this court should consider a range of other factual bases (i.e. in addition to, or other than the timing issue) which could support Adv Mpshe’s conclusion, and which were raised in the representations made on behalf of Mr Zuma. This argument is made even though Mr Zuma has refused to make these representations available at any stage of these proceedings; and even though Adv Mpshe specifically indicated that he rejected these contentions in the representations," the DA submits.In October 2016, the Constitutional Court refused the NPA's appeal, saying it would not be in the interest of justice to hear it before the SCA.