Fifteen Degrees: How Cricket Turned the Throwing Law from an Umpire’s Call into a Lab Test

Few laws in cricket have ended as many careers, or caused as many arguments, as the one that separates bowling from throwing. For more than a hundred years it was enforced by an umpire watching from the middle. Since early 2005 the decisive judgement in international cricket has been made in a laboratory, against one number: fifteen degrees of elbow extension. This piece explains how cricket got from one system to the other, and what the change does and does not settle.

What the law actually says

The Laws of Cricket do not ban a bent arm. They ban straightening it. Under Law 21.2, a delivery is fair in respect of the arm if, once the bowling arm has reached the level of the shoulder in the delivery swing, the elbow joint is not straightened, partially or completely, from that instant until the ball has left the hand.

International cricket adds a measurement on top of that principle. The ICC playing conditions define an illegal bowling action as one in which the bowler’s elbow extension exceeds 15 degrees, measured from the point at which the bowling arm reaches the horizontal until the point at which the ball is released. Any hyperextension of the elbow, a bend backwards beyond straight that some bowlers naturally have, is discounted.

The era of the umpire’s eye

Before laboratories, the only test was whether an umpire was prepared to call a no-ball. Some were, and their decisions became landmarks.

• Ernie Jones, 1897-98: During the Ashes series of that Australian summer, umpire Jim Phillips no-balled the Australian fast bowler Ernie Jones for throwing in the Melbourne Test, the first time a bowler had been called for throwing in a Test match. Jones had already been called earlier that season, in South Australia's match against the English tourists.
• Geoff Griffin, 1960: In the second Test at Lord's, which began on 23 June 1960, the South African fast bowler took a hat-trick, dismissing Mike Smith, Peter Walker and Fred Trueman, and was repeatedly no-balled for throwing by umpire Frank Lee. He was called again by Syd Buller in an exhibition match played after the Test finished early. He never played another Test.
• Ian Meckiff, 1963: On 6 December 1963, in the first Test against South Africa at Brisbane, umpire Colin Egar called the Australian left-armer on the second, third, fifth and ninth balls of his only over. His captain, Richie Benaud, took him off, and Meckiff retired at the end of the match. He finished with 45 wickets in 18 Tests.

These cases share a pattern. The judgement was made live, by one person, in front of a crowd, and the consequences were usually final. There was no test a bowler could take to prove the umpire wrong.

Muralitharan and the limits of the naked eye

The case that exposed the weakness of that system began on 26 December 1995. On the first day of the Boxing Day Test at the Melbourne Cricket Ground, umpire Darrell Hair no-balled Sri Lanka’s off-spinner Muttiah Muralitharan seven times for throwing. The other umpire, Steve Dunne, did not call him, and Muralitharan went on bowling from Dunne’s end without further calls.

Muralitharan bowls with a bent arm. The question was whether that arm was being straightened during delivery, or only looked as if it was. In the end it was biomechanical analysis, rather than an umpire, that decided the matter, and the ICC cleared him.

That episode, and others like it, pushed the game towards measurement. By the late 1990s the ICC was working with tiered tolerance levels: 5 degrees of elbow straightening for spinners, 7.5 degrees for medium-pace bowlers and 10 degrees for fast bowlers. In 2004 Muralitharan’s doosra was tested and found to exceed the five-degree limit for spinners. Soon the tiered system itself would be put to the test.

The study that changed the number

Biomechanists Bruce Elliott, Marc Portus and Paul Hurrion analysed bowlers at the 2004 Champions Trophy for an ICC sub-committee of former Test cricketers that included Michael Holding. The finding, released in November 2004, was blunt: virtually all bowlers straightened the elbow to some degree. Bowlers long regarded as having clean actions, including Glenn McGrath and Shaun Pollock, were among them. The only bowler tested who stayed under the five-degree mark was the West Indies batter Ramnaresh Sarwan.

The reasoning was that some straightening is a normal part of bowling, and that below about 15 degrees it is unlikely to be seen without instruments. The ICC accepted a single 15-degree limit for bowlers of every speed, and it was adopted by the ICC’s chief executives in early 2005.

How the system works now

Under the current playing conditions, an umpire or match referee who suspects an action completes a bowling action report form at the end of the match, and the bowler is then assessed under the ICC’s illegal bowling regulations. The measurement takes place away from the field, not during play. A bowler found to be over the limit is suspended from bowling in international cricket until the action is remedied and passes a fresh assessment.

The best-known example of the modern process is Pakistan’s off-spinner Saeed Ajmal. On 9 September 2014 the ICC suspended him from bowling in international cricket with immediate effect, stating that all of his deliveries had exceeded the 15-degree tolerance. He had previously been reported in 2009 and cleared.

What fifteen degrees settles, and what it does not

What follows is interpretation rather than a record of decisions. The 2005 reform did two things at once. It ended the idea that a perfectly straight arm was the norm, because the measurements showed it was not. And it moved the decisive judgement from the middle of the field to the laboratory, which helps explain why dramatic on-field calls of the Griffin and Meckiff kind have become rare in international cricket.

It did not end argument. The law still rests on the elbow straightening, which can only be measured precisely off the field, while umpires in a match must still decide whether to report what they see. The number itself is a line drawn from evidence about what the eye can detect and what bowlers normally do, not a natural boundary. The 15-degree rule is best understood as a workable compromise: one that protects bowlers from being judged on appearance alone, while still giving the game a clear point at which a bowl becomes a throw.