A form of investigative journalism where a journalist assumes a false identity for the purposes of gathering information. Often involving deception, it can expose hidden truths and wrongdoing — from the exploitation of vulnerable people to corporate corruption. It’s a controversial and sometimes dangerous tool, and it’s critical to know where the legal lines are before launching an undercover report.

In a world where few countries have strong transparency laws or strong protections for journalists’ sources, going undercover is one of the most powerful tools reporters have to uncover public interest stories. This GIJN guide, with advice from seasoned investigative journalists and examples of great undercover reporting from around the world, offers tips for using this technique effectively and responsibly.

Undercover report can be a valuable tool for revealing complex issues, from human trafficking to illegal gambling and political corruption. But it should be used only when other methods have failed to gather the necessary evidence. And when it is used, it should be transparent with audiences and clearly explained in reports, to avoid accusations of entrapment or misleading viewers.

The earliest and most influential examples of undercover report came from women, like Nellie Bly’s harrowing experience posing as a psychiatric patient to expose institutional brutality in the late 19th century. Today, it’s still important for women to use this technique – and also other forms of subterfuge – to expose hard-to-penetrate institutions and situations that deserve the public’s attention.