The New Zealand Law Society is calling for a comprehensive reassessment of security levels and measures in our courts.

It follows an incident in Nelson this week when a cell phone was thrown at the head of a Crown Prosecutor.

The Society believes it's a very serious breach of courtroom security.

The prosecutor has been off work since Monday's incident, in which the phone broke apart when it hit her head.

Society spokesperson Mark Wilton said lawyers should be free to appear in court without fear of assault or injury.

He wants a comprehensive reassessment of courtroom security levels and measures.