Metadata remains a controversial subject for lawyers. Typically defined as "data about data," the term refers to a hidden layer of information within an electronic document. Most metadata is relatively benign, providing only basic information about a document's authorship. More dangerous information can also lurk below the surface, however, including track changes and comments.

A number of bar associations have weighed in on the subject of metadata. The ethics opinions issued typically revolve around three questions: What is an attorney's duty when sending an electronic file? May an attorney search (or "mine") electronic documents he or receives for metadata? And finally, if a receiving attorney discovers potentially compromising metadata within a file, must he or she notify the sender?

The answers to these questions have been mixed and often hang on nuance. We've prepared a comparison chart of all current metadata opinions, with links to the opinion language where available. The chart includes the two newest opinions - Pennsylvania and West Virginia:

• Pennsylvania Bar Association Formal Opinion 2009-100 (available online for PBA members), which replaces an earlier opinion on the same subject issued in 2007. The 2009 opinion suggests that sending attorneys have a duty of reasonable care to avoid inadvertently transmitting confidential information via metadata, but the opinion is less clear on the recipient's duties. The opinion lists several factors that recipients must weigh in determining whether they may look for or use metadata. On the question of notice, the opinion is clear: if they the recipient determines that metadata was included inadvertently, the attorney must "promptly notify" the sender.
  
  
• West Virginia Bar Association Legal Ethics Opinion 2009-01 (PDF). The West Virginia opinion takes a similar stance on the sender's duty. On the recipient's duties, the committee focused on actual knowledge: if the recipient has actual knowledge that metadata was sent inadvertently, then he or she should not review the metadata before consulting with the sender. The opinion suggests that recipients err on the side of caution when it is unclear whether metadata was included inadvertently. Finally, regarding notice, recipients should consult with the sender before reviewing metadata if they have actual knowledge it was included inadvertently or if there is doubt as to whether the metadata was sent inadvertently.

Visit out metadata ethics opinion comparison chart for more complete summaries of all current ethics opinions regarding metadata.