Builder George Collier was found guilty of gross negligence manslaughter at Mold Crown Court in a case brought by the Crown Prosecution Service. His company, Parcol Developments Ltd, pleaded guilty to breaching the Health and Safety at Work Act 1974 at an earlier hearing.
The court heard that Collier was doing construction work outside a house in Ffordd Penrhwylfa, Meliden in Prestatyn on 26 July 2008 when three-year-old Meg Burgess and her mother, Lindsay Burgess, were walking in front of it on a public footpath.
An investigation by North Wales Police and the Health & Safety Executive (HSE) found the wall had recently been built and had been backfilled by Collier shortly before it collapsed, killing Meg, who was walking behind her mother.
The wall was acting as a retaining wall but had not been designed or constructed for this purpose and fell under the weight of the earth stacked up against it.
Speaking after the hearing, HSE inspector Debbie John said: "This was an entirely preventable incident that resulted in the tragic death of an innocent three-year-old girl. There were basic failings in the way that George Collier and Parcol Developments Ltd. planned and managed the construction of the wall, leading to its collapse.
"On the day of the incident George Collier and Parcol Developments Ltd backfilled the wall despite knowing that retaining walls should be designed by a specialist structural engineer. Neither had engaged a structural engineer to design a safe retaining wall.
"This case is an important reminder to those working in construction to make sure that design work is done by competent people and building is done to the appropriate standard. It also highlights the importance of ensuring that members of the public are kept away from construction work."
Rosemary Ainslie, lawyer for the CPS Special Crime division, said: "This was a tragic case, in which a young girl lost her life.
"Mr Collier was responsible for the design and construction of the wall but did not make sure it was built to safe standards, nor did he prevent members of the public from walking past it, with terrible consequences.
"The jury has found Mr Collier guilty of gross negligence manslaughter and his conviction should act not only as a reminder of the dangers of sub-standard building work but also of the consequences for those who carry it out.”
George Collier, 49, of Llys Glan yr Afon, Kinmel Bay pleaded not guilty to charges of gross negligence manslaughter December 2011. His company, Parcol Developments - of the same address - pleaded guilty to breaching Section 3 (1) of the Health and Safety at Work Act 1974 at the same time. No additional penalty was given to the company.