The dispute between the ICC and the University of Western Australia (UWA), which was previously the sole laboratory for testing bowlers with suspect actions, centres around the loopholes that UWA says can be found in current testing procedures, and the impact of technical issues on the bowlers under scrutiny.

The chief concerns, raised by Jacqueline Alderson, associate professor in biomechanics at UWA, are:

  • The method of judging the moment of ball release - and whether this could disadvantage spin bowlers
  • The repercussions of placing markers in different places
  • The influence of both elbow 'flexion' and 'extension'
  • The continued use of 2D imagery in testing

Identifying the frame of ball release

Alderson says that in tests conducted on Ajmal in 2009, the 'frame of ball release' was crucial in establishing the legality of his action. "More than any other bowler we have tested," Alderson said, a large number of Ajmal's deliveries would have been illegal in the 2009 testing if the point of ball release was identified to be "1-2 frames or 0.004-0.008 seconds later".

UWA conducted a study after the Ajmal tests and found that the most reliable way to identify the point of ball release for spinners was by using synchronised high-speed video (with the 3D system). The method developed at the UWA to automatically identify the ball release frame (by identifying a change in the distance between markers placed on the ball and the hand) can reliably be used for fast/medium pace bowlers, but it is not so with spinners. "As spin bowlers release the ball out of different parts of the hand, which may or may not involve the fingers, any automated marker tracking method should not be used to identify ball release," Alderson said.

Should ball-release parametres and tracking methods be arrived at by "automated" methods of testing, Alderson said, it would "significantly disadvantage spin bowlers". She added that, "ball release identification would however not affect the legality findings of current ICC reports using the 'new model', given the extremely high elbow extension ranges that are being reported."

The repercussions of placing markers in different places
Alderson said that there were multiple ways/permutations by which the markers placed on the arm could calculate an elbow angle. The UWA had measured elbow extension by assessing the same delivery with three very slightly different models of marker placement. In Ajmal's case, Alderon said, two models found the delivery to be legal and one illegal, with a six-degree difference in the extension range calculated.

It meant that the modelling approach could itself "result in false positives and negatives, and if you are a bowler facing suspension, the difference can be catastrophic". UWA objected to the fact that the ICC had not released the modelling approach being used to calculate the angle in the new model to outside parties. Alderson said this prevented individual bowlers and home boards from getting independent feedback about the effectiveness of remediation coaching.

The continued use of 2D imagery in testing, and the problems of relating actions in tests to in-match actions
Disagreements exist about the methods used in testing to try to ensure an action replicates that which is used in matches - which is determined by comparing the actions in tests to 2D television footage. Alderson does not believe it is appropriate to compare 3D biomechanics tests with 2D television footage in order to determine if a bowler is replicating his in-match action. Her opinion on the process is clear: "If 2D footage is deemed to be reliable for this purpose [examining an action] then the ICC should simply use this approach during in-game assessments." The reliance on 2D comparison in the testing procedure is, she says, "inconsistent with the view that it is prone to perspective error and the subjective interpretation means it should not be used to make in-match legality determination."

It is the duty of any biomechanics team, she says, "to provide opinion on the validity of the match-lab replication in the final report, as was previous practise. This provides an avenue for the biomechanics team to provide feedback to the committee and for the testing to be declared not representative and therefore invalid."

Considering elbow flexion as well as extension, and expanding research into bowling actions

This is a highly contentious field where there is no unified view, and analysis of elbow flexion (the closing of the elbow joint) as well as extension (the straightening of the elbow joint) would lead to the throwing law becoming even more complex.

The flexing of the elbow can offer, Alderson says, just as much advantage (if not more) than elbow extension in some bowlers. This was something that was not considered when the initial attempts were made to quantify the mechanical difference between throwing and bowling, she said, and it was then decided that throwing was best characterised by the presence of elbow extension whereas bowling was not. The next step was then to decide how much extension characterises throwing and hence some baseline extension-tolerance levels - the 15-degree rule, included - were established for bowling.

In Alderson's opinion, "the original intention of the law is likely that the bowler should 'keep the arm straight and not throw the ball'. Or alternatively, that the arm should not change flexion-extension orientation (elbow angle) once the forward swing commences - it should neither extend nor flex but remain relatively fixed/stiff/stable." However, she believes that throwing should be assessed from a multi-dimensional viewpoint instead of a "single-axis measurement" of 15 degrees.

UWA believes this is possible by conducting research into using computer modelling methods in match situations - this could specifically finetune the definition of a legal delivery. "We have conducted a pilot study which shows this type of approach [computer modeling of bowlers' actions] is feasible and can allow us to compare 3D lab versus match footage directly as an initial first step."

Alderson says assessing a large data base of bowlers using 'computer vision methods' would help determine a threshold of "maximum allowable change in the shape of the bowling arm at the elbow and use this threshold to [more accurately] define a legal delivery."

The "3D arm-shape assessment" can be explained in simple terms, Alderson says. "If a bowler displays a posture that resembles a throw (think of a javelin-throwing position) then we should be attempting to assess if there is overall three-dimensional orientation change to the trunk, upper and lower arm. If so, then the bowler is likely not delivering the ball legally."

The ICC has made a significant investment "in replicating the wheel (developing marker-based modelling) to roll out status quo technology (lab-based, marker-based motion capture)." In the UWA's opinion, this is "a retrograde step that does nothing to advance the science of this issue for the game".

George Dobell is a senior correspondent at ESPNcricinfo