The court-martial of a highly decorated Navy SEAL platoon leader on war crimes charges has been thrown into turmoil by, of all things, a harmless-looking image of a bald eagle perched on the scales of justice.

The bit of digital artwork, embedded in an email message, contained hidden software that could track if anyone read or forwarded the email, and may have also been able to allow access to all communications and files on the recipients’ computers, defense lawyers argue in court filings.

The email was sent last week to defense lawyers representing Special Operations Chief Edward Gallagher by the lead Navy prosecutor in the murder case against the chief, apparently with the judge’s approval. The tracking software was also included in emails sent to lawyers for the chief’s commanding officer — Lt. Jacob Portier, who is charged in a related case — and to a journalist for Navy Times covering both cases.

Furious at what they see as an improper attempt to spy on them, the defense lawyers are demanding an investigation, and the suspension of proceedings against both men while it is conducted. Chief Gallagher’s trial is currently scheduled to begin May 28.