Jon Johansen, 20, is accused of breaking Norwegian law by cracking DVD codes and helping others copy films.
In January this year, he was acquitted after courts said he did not break the law when he created his DeCSS system.
The case is seen as a major test of Norway's computer protection laws, and a verdict is expected in early 2004.
The case sparked fierce debate between consumer rights campaigners and the copyright industry.
Media and film industry representatives want tighter restrictions on copying, including more digital rights management software to prevent unauthorised copying of CDs and DVDs.
This has angered campaigners because they say it prevents people from making legitimate back-ups of data.
It is claimed that piracy costs the US film industry about $3 billion (£1.7 billion) every year in lost sales.