Laboratory conditions are better but less realistic

For the last century, bending the elbow has been one of the most frowned-upon methods of cheating in the game.

But technology shows most elbows involuntarily flex during a delivery.

The International Cricket Council (ICC) is determined to define a new line to divide black and white, by filming hundreds of deliveries from more than 100 top bowlers.

"There is the odd freak who's got an elbow joint which is very rigid where the amount of arm-straightening is negligible," ICC general manager David Richardson told BBC Sport.

But with most bowlers, he said: "With the forces on the arm in the bowling action there is a degree of straightening.

"You'll be watching and thinking: There's nothing wrong with his action. But actually there's 10 or 12 degrees of arm-straightening."

A competitive match situation guarantees the correct levels of player effort and technical application Dr Paul Hurrion Human movement specialist

Research has already been done into fast bowlers but the recent controversy surrounding Sri Lanka's Muttiah Muralitharan has revealed a lack of knowledge regarding spinners.

Slow bowlers will be under the spotlight in a programme that began during the Edgbaston Test between England and West Indies and will continue during the ICC Champions Trophy.

High-speed cameras positioned behind the bowler's arm and square of the wicket film at 250 frames a second - five times faster than TV cameras.

Computer software then combines the footage from both cameras to create a three-dimensional image.

It is a similar model to that used when Muralitharan's action was analysed, except that this version will be in the field rather than a laboratory.

The bottom line still is the umpires on the field and the match referee David Richardson ICC general manager

The man in charge of this project, Dr Paul Hurrion, helped England's James Kirtley and West Indies pace man Jermaine Lawson remodel their actions.

He explained: "A competitive match situation guarantees the correct levels of player effort and technical application in the most realistic conditions."

Current guidelines allow spinners a tolerance of five degrees - half that allowed for fast bowlers - but Richardson admits that may be wrong.

"The idea is to look not only at the guys we think are suspect but to look at all spinners," he said.

"We don't want to be taken by surprise to find that a guy we've always though had a legal action - a Shane Warne or an Omari Banks - is actually bowling at 10 degrees."

Muralitharan has currently been advised not to bowl a delivery he invented last year - know as a doosra - which requires up to 14 degrees of flexion.

But he has been under constant scrutiny through his career because of a congenital deformity in his elbow, which cannot straighten.

Muralitharan's action is regularly under scrutiny

"I've every sympathy for Muttiah because when you watch him you think he's straightening his arm by 30 or 40 degrees," said Richardson.

"But his action - where he starts with a bent arm and it stays bent - from a 2D perspective creates the illusion of throwing to a much greater extent."

The Australian scientist who worked with Murali claims the action should not be judged illegal even though it breaches the current limit.

And this research - the most extensive ever carried out in this area - could see those guidelines changed.

Even though there are high-tech cameras on the field, though, bowlers should not feel under pressure as this work is for research purposes only.

"The bottom line still is the umpires on the field and the match referee," Richardson said.

"Their brief is to report someone only if his action appears suspect to them using the [naked] eyes so bowlers of today are treated the same as bowlers of yesteryear."

Most bowlers of yesteryear, though, would have choked at the idea their elbows were bent.