A fireworks contractor in charge of a display held on the night of a massive motorway crash in which seven people died and 51 were injured has been cleared of breaching health and safety laws.

A judge directed a jury at Bristol Crown Court to find Geoffrey Counsell, 51, not guilty of a single charge of failing to ensure the safety of others contrary to the Health and Safety at Work Act.

The charge alleged that Mr Counsell, of Ashill in Somerset, failed to ensure he operated the firework display so as to ensure, as far as was reasonably practicable, that others who might be affected were not exposed to risks to their health and safety.

Mr Counsell was originally charged with seven counts of manslaughter but they were dropped earlier this year and instead he faced the health and safety charge.

Seven people died in a massive motorway pile-up involving more than 30 cars when they were engulfed by a thick fog on the M5 near Taunton at around 8.20pm on November 4 2011.

Grandparents Anthony and Pamela Adams, from Newport, South Wales; father and daughter Michael and Maggie Barton, from Windsor, Berkshire; battle re-enactor Malcolm Beacham, from Woolavington, Somerset; and lorry drivers Terry Brice, from South Gloucestershire, and Kye Thomas, from Cornwall, died and 51 people were injured, including some seriously, in the pile-up.

The smog was so thick that motorists on the northbound carriageway likened it to having a tin of paint thrown over their windscreens.

Mr Counsell, who ran Firestorm Pyrotechnics, was the contractor hired by Taunton Rugby Club to run the £3,000 display at its ground, which was watched by 1,000 people.

He set off 1,500 shots as part of his Jupiter Display in 15 minutes - just 200 yards from the motorway.

In a leaflet promoting his business, the experienced Mr Counsell described the display as the "biggest and most lavish" piece of "unforgettable" pyrotechnics he offered.

Witnesses described seeing the smoke drift across the nearby carriageway.

Peter Blair QC, prosecuting, told the jury: "Essentially the prosecution say they experienced a loss of visibility, generated, we say, by a plume of smoke created by Mr Counsell from his firework display which had built up.

"It was dispersed because of the lack of wind mixed with the humid air and drifted in the direction of the motorway.

"We say people were exposed to an appreciable risk to their personal safety that night as a consequence of the way Mr Counsell prepared for and then went about his business.

"We say that ensuring the safety of people using that motorway needed particular care if you were going to undertake a big firework display involving the use of a substantial volume of these hazardous explosives, which generated a lot of smoke.

"Smoke can have an appreciable effect on reducing visibility - that should be obvious. It didn't take long from the build-up of smoke to the dramatic loss of visibility.

"We say if he had adequately undertaken his health and safety properly, some or all of the consequences which unfolded on November 4 may have been avoided."

Adrian Darbishire QC, representing Mr Counsell, said witnesses described seeing smoke drifting away from the motorway.

"You will see many witnesses are absolutely clear that what they saw, and indeed in some cases what they drove through, was not smoke nor smog but fog," he said.

Mr Justice Simon ruled yesterday that Mr Counsell had "no case to answer" following an application from the defendant's barrister at the halfway point in the trial.

The judge said the prosecution's case was based on "hindsight" and there was not sufficient evidence to show that Mr Counsell ought to have foreseen that smoke from the display could have drifted and mixed with fog to create thick smog.

"In my view, the prosecution case is heavily weighted with hindsight," the judge said in his ruling.

"I have therefore concluded that the evidence is such that the jury cannot continue in these circumstances and it is my duty to stop the trial and order an acquittal."

The foreman formally found Mr Counsell not guilty and he was discharged.

Mr Justice Simon explained to the jury of eight men and four women why he was directing them to acquit Mr Counsell.

He said that smoke from fireworks, unlike bonfire smoke, had never before been regarded as a hazard and therefore Mr Counsell could not have foreseen what happened.

"I concluded therefore that the prosecution case did not pass the threshold for you to be sure the defendant, Mr Counsell, was guilty," he said.

"The prosecution case was dependent on hindsight and consequence rather than foresight and risk."