The acquittal of Momčilo Perišić (former Chief of the Yugoslav Army General Staff, right hand of Slobodan Milošević during the Balkan wars) received a loud echo both in the affected countries and in the international media in 2013. His acquittal was based on an Appeal Judgement including an unconvincing interpretation of aiding and abetting liability. The author of the present paper discusses the judicial reasoning provided by the Appeals Chambers of the ICTY before the Perišić Appeal Judgement was delivered and demonstrates how negligence of judicial chambers can build case law which leaves the door wide open to highly debatable judicial conclusions. The paper briefly presents the 14-year story of the application of the concept of aiding and abetting liability by the ICTY Appeals Chambers, from the 2000 Aleksovski Appeal Judgement to the 2014 Sainović Judgement.