that simple circular out what they are stating is that there s a 90% reported evidence of something being found. does that mean there was not evidence found. that leads to the next kind of obvious follow up question. if it is so difficult to work out whether a shot has actually been fired on the ground how does shot spotter know with such confidence that it s 97% accurate? shot spotter told the bbc it works out its accuracy from police reports on the ground listening to gunshots, telling shot spotter when they got it wrong. we telling shot spotter when they got it wronu. ~ , ., ., it wrong. we rely on ground truth from agencies it wrong. we rely on ground truth from agencies to it wrong. we rely on ground truth from agencies to tell it wrong. we rely on ground truth from agencies to tell us - it wrong. we rely on ground truth from agencies to tell us when - it wrong. we rely on ground truth from agencies to tell us when we | from agencies to tell us when we mess. missed detection