Poznan on the 28th of June 1956 witnessed a demonstration initiated for economic reasons, which transformed itself into street riots pacified by the army. Fifty seven people died on the spot or of their wounds in hospitals and over eight hundred were arrested. Following these events, in September 1956 the authorities inaugurated trials of the riot participants. The line of defense was constructed on the expert opinions provided by three eminent Polish sociologists: Józef Chalasinski (1904-170) and Jan Szczepanski (1913-2004) from the University of Lódz and Tadeusz Szczurkiewicz (1895-1984) from the Adam Mickiewicz University in Poznan. Józef Chalasinski's opinion proved to be the most important one for the trial. He pointed to the fact that the protesting one-hundred-thousand-large crowd on that day had huge power of psychological influence on the participants and, thus, the participation in anti-regime riots was the effect of a moral impulse. Expert sociologists and psychiatrists, who played a major role during the trials of 1956, are currently marginalized and not given enough recognition in scholarly literature.