On appeal, the Supreme Court ruled there was insufficient evidence to prove that the 15 were members of a terrorist group, as the lower court held.
The 20 men, mainly Algerians and Moroccans, were convicted by the National Court last February of Islamic terrorist activity. None was found guilty of the more serious charge of plotting to destroy Madrid's anti-terrorism courthouse with a truck bomb.
The other four are two convicted of membership in a terrorist group and two convicted of the lesser charge of collaboration with a terrorist group. The Supreme Court also upheld their sentences, which range from five to 10 years.