A district court in Gdansk Tuesday overruled an earlier judgment that Adam "Nergal" Darski, the lead singer of Behemoth, was expressing artistic freedom during the 2007 concert, Polskie Radio reported.
Darski also said during the concert the Bible was "full of lies," and members of the audience burned its pages.
The singer's lawyers had argued during the initial trial in 2011 the concert was attended only by fans who were not offended by Darski's actions.
A person could be guilty of offending religious sensibilities even if they had not "directly" intended to do so, Poland's Supreme Court ruled in October.
The verdict in the second trial is expected to be a major ruling on freedom of speech in Poland.