In cricket, if a spinner bowls a full toss that hits the batsman on the pads without pitching on the ground & in this case a DRS (Decision Review System) is requested by either party, how does the ball tracking work?

Assume that, the ball hits the bottom of the pads so that it would have definitely hit the ground & spun a little before going beyond(or through) the stumps. How does the DRS's ball tracking technology decide how much spin to add to the ball "tracking" portion of the review.

It is easy in case of a fast bowler, the ball will hold its line, so it can be tracked accurately. But what other factors are considered in the algorithm in case of a spinner, especially when its a full toss.

Note that I am not concerned if the batsman is out or not, so this question is not a duplicate of LBW to a spinner's full toss

2 Answers 2


Hawkeye doesn't care what type of delivery a bowler normally gives, as any bowler can give a huge amount of variation on the delivery. It only tracks actual movement.

In the case that the ball hits the batsman on the full, it will assume a continued line but will not extrapolate any bounce path and will not provide information on the height of the ball at the wickets.

This is specified in the Playing Conditions, for example in Appendix D Decision Review System (DRS) and Third Umpire Protocol, part 3.4 Review of LBW Decisions:

When the ball strikes the batsman on the full, and the evidence provided by the ball-tracking technology indicates that the ball would have pitched before striking or passing the wicket, there will be no information available from that delivery that will allow the ball-tracking technology to accurately predict the height of the ball after pitching.

With regard to determining whether the ball would have hit the wicket under these circumstances, the ball-tracking technology shall project the line of the ball in accordance with clause 36.2.3 (it is to be assumed that the path of the ball before interception would have continued after interception, irrespective of whether the ball might have pitched subsequently or not), and display the simulated path of the ball from directly above the wicket.

The following paragraph then specifies that the umpire will be shown the line of the ball (i.e. whether it was going towards or besides the wicket only) and that any judgement of height is left to the bowler's end umpire.

  • I would much appreciate a citation or even a video of such event happening during a match Feb 24, 2018 at 4:05
  • We don't need video when the playing conditions are very clear.
    – Nij
    Feb 24, 2018 at 4:46

As per the answer to the LBW to spinners full toss the ball is assumed to have carried on upon its trajectory without change. So no spin is to be included. This is shown in law 36.1.5 and 36.2.3 LBW

As Ball tracking relies on the ball continuing to do what it was doing then the predicted path would be as per the law what the ball would have continued to do. So it would be fine to use for line.

There is an argument for saying that the bounce of the ball could not be predicted where the path of the ball show it pitching before the stumps.

  • Can you cite the law that mandates that ball tracking should follow the line & not add a spin for unavailable portion Feb 24, 2018 at 4:06
  • More than an argument - the playing conditions say it cannot, and must not be used to provide information about any bounce that may or may not have occurred.
    – Nij
    Feb 24, 2018 at 4:45
  • @KharoBangdo no law, the law says the umpire shall assume the ball will carry along the path it was taking. Fundamentally all ball tracking does is assigns an equation to the flight of the ball and uses it to predict future path, this will in the case of a full toss have the ball carrying along the same path.
    – Ben Whyall
    Mar 4, 2018 at 22:49

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