The Supreme Court has been told information about juries provided by police threatens the impartiality of juries and causes the administration of justice to seriously malfunction.
The case was sparked by the conviction of Deborah Gordon-Smith on drugs charges including conspiracy to supply.
Ms Gordon-Smith's appeal is over the information which provided in order to vet juries.
Opening submissions on her behalf, lawyer Gerry McCoy said the police provide crown prosecutors with information about people on a jury list, including any convictions, acquittals and their exposure to crime.
He said police also give what he called unverifiable intelligence such as a potential juror's association with known criminals.
Mr McCoy told the court this information is not made available to the defence and is clandestine and unaccountable.
He said it causes the administration of justice to seriously malfunction, turning a jury which should be impartial into one which favours the prosecution.