The 15° rule, explained
Under Law 24.3 of the Laws of Cricket, a delivery is called illegal if the bowler's elbow straightens by more than 15 degrees between the moment the bowling arm reaches shoulder height and the moment the ball is released — regardless of where the arm or wrist is pointing at release.
It's a measurement of joint movement during the action, not the final arm position — which is exactly why it's so hard to judge by eye, even for experienced coaches and umpires. Most flagged actions aren't deliberate; they're a biomechanical habit that built up unnoticed, often from a young age.
Why it matters beyond the rule itself
- Being called for throwing mid-match is one of the more demoralising things that can happen to a young bowler, usually with no warning beforehand.
- The same mechanics that risk an illegal call often load the elbow and shoulder in ways that raise injury risk over a season, not just a single delivery.
- Club-level coaches watch technique — rhythm, run-up, release point — because that's what's visible in real time. Elbow extension happens in a fraction of a second; it needs frame-by-frame video to actually see.
How SportScan checks it
Point a phone camera at a bowler from the side during a normal net session. SportScan's pose-tracking model follows the bowling arm frame by frame through the delivery swing and estimates elbow extension against the same 15° reference the Laws use — along with the rest of the bowling action (run-up rhythm, front-arm/hip sequencing, follow-through) in the same session.
Every video is processed on your own device and analysed in the moment — nothing is uploaded or stored on a server. You get coaching cues in plain language, not a raw angle number to interpret yourself.