The modern “Citizens’ Jury” label is strongly associated with political scientist Ned Crosby, who developed the process idea in the early 1970s and went on to found the Jefferson Center as a vehicle for research and real-world trials.
Early pilots in the 1970s used the jury metaphor to make deliberation legible: ordinary citizens, evidence, witnesses, facilitated discussion, and a considered collective statement at the end - cndp.us 
nedcrosby.org
In parallel, a closely related European lineage emerged via German Planning Cells (Planungszelle), associated with Peter Dienel, also developed in the early 1970s as a structured way for randomly selected citizens to produce a “citizens’ report” for public decision-makers.
The two traditions are often described as near-siblings: similar design logic, similar time-boxing, and similar emphasis on facilitated evidence-based deliberation, even when the branding differs - participedia.net eprints.soton.ac.uk
By the 1980s and 1990s, citizen juries became one of several recognizable “standard forms” of deliberative engagement alongside things like the Consensus Conference.
Over time, they spread into policy domains where legitimacy depends on more than a survey (e.g. technology controversies, health priority-setting, local planning disputes) and where decision-makers want a visible, reasoned public judgment rather than just “views.” - journals.openedition.org iied.org