Article: The 15-year-old's body was found on a school playing field in Flint in 1976.
A man was jailed for 12 years after admitting manslaughter. However in September 2016, Stephen Hough, 57, was charged with her rape and murder.
Police voluntarily referred the case to the Independent Police Complaints Commission (IPCC).
The IPCC will look at whether officers in the initial investigation acted in accordance with the rules in place at the time relating to the detention and interviewing of suspects.
It will also investigate how the force handled new information that came to light in 2006.
IPCC Commissioner for Wales, Jan Williams, said: "This will be a complex investigation not least because of the passage of time, but it is important for all concerned that we independently investigate the case."
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Summarize: Police watchdogs are investigating how North Wales Police handled the inquiry into the rape and murder of schoolgirl Janet Commins over 40 years ago.
Problem: The latest retail sales index showed Scottish sales rose by 0.8% in value in the fourth quarter, compared with a country-wide figure of 1.5%.
The volume of sales north of the border rose by 1.7%, compared with 2.3% for Great Britain as a whole.
On an annual basis, Scotland lagged behind Great Britain in both volume and value terms.
In terms of volume, Scottish sales showed a year-on-year rise of 1.6% in the final quarter, compared with a rise of 5% for all of Britain.
Large shops with at least 250 employees - which account for about 70% of retail industry sales - saw an increase of 0.9% in sales volumes, compared with the previous quarter.
Sales at small and medium stores grew by 3%.
Commenting on the figures, Euan Murray of Barclays Corporate Banking said: "The extravaganza of planned promotions in November, as well as a last-minute dash in the days before Christmas provided a boost to the sector, resulting in an increase in sales volume in Scotland on both the previous quarter and year-on-year.
"Non-food products such as clothing fared particularly well towards the end of 2014, and now that the spring ranges are on the shelves, fashion retailers will be hoping for milder weather to encourage shoppers to freshen up their wardrobes with the new lines."
Scottish Retail Consortium director David Lonsdale said: "The resumption of growth in retail sales in the final quarter of last year is encouraging, aided by falling prices at shop checkouts and at petrol pumps.
"The recovery in consumer confidence remains fragile however, and brings into sharp focus big upcoming public policy decisions which could affect disposable incomes and take home pay, notably the first minister's proposed replacement of council tax and the setting of the Scottish rate of income tax.
"These decisions must support consumer spending and economic growth."
Deputy First Minister John Swinney said: "The latest official Retail Sales Index for Scotland for the final quarter of 2014 showed that the retail sector in Scotland continued to grow over both the three-month period and the past year.
"Looking at the wider economy, Scotland now has the highest jobs figures in history, the highest female employment in history, the lowest level of unemployment since the end of 2008, lower unemployment than the rest of the UK and higher employment and economic activity."
Scotland Office Minister David Mundell said: "It is encouraging to see retail sales in Scotland increasing over the final quarter of 2014 and over the year.
"The UK is now the fastest growing economy in the western world and the decisions made by this government mean the country is on course to prosperity with higher growth, record employment, lower unemployment and a falling deficit.
"Scottish businesses have helped make this happen and they are benefiting from being part of a strong and diverse UK economy."
What was that article about?

A: Scottish shop sales rose at the end of last year but lagged well behind the UK as a whole, according to new figures.
Leo, four, was on holiday with family in Melbourne when he spotted the machine in a hotel lobby.
Reports said the boy was attempting to reach a packet of biscuits when his arm became stuck in anti-theft mechanisms.
He was sedated and distracted with smartphones while emergency crews worked with angle grinders to cut open the machine.
Witnesses said they could hear his screams from the street.
The boy was taken to the Royal Children's Hospital in a stable condition.
Leo's father Aaron Shorthouse said the experience was very hard on his son.
"We live up in Arnhem Land, Northern Territory, and I don't think he's seen a vending machine before, so he saw the Oreos, and some biscuits and a few other things," Mr Shorthouse told local media.
Arnhem Land is a remote region of the Northern Territory with a population of just 16,000 stretched across 97,000 square kilometres (37,000 square miles).

Sum: A boy from Australia's remote far north spent six hours stuck in the first vending machine he had ever seen.
Problem: The ancient Chinese art improves physical performance and enhances quality of life, say researchers.
Tai Chi combines deep breathing and relaxation with slow and gentle movements.
The study, published in the British Journal of Sports Medicine, suggests the exercise helps with pain and stiffness in arthritis.
It can also help improve quality of life in the lung condition, chronic obstructive pulmonary disease (COPD).
And it may have some physical benefits for people with breast cancer or heart failure, according to researchers from the University of British Colombia, Vancouver.
In the future, it might even be possible to consider prescribing Tai Chi for patients with several illnesses, they said.
"Our findings support the results of a previous systematic review that showed the effectiveness of Tai Chi on health outcomes in older patients with chronic conditions," Dr Yi-Wen Chen and colleagues wrote in their research paper.
"Tai Chi can improve some physical performance outcomes in four chronic conditions (cancer, osteoarthritis, heart failure and COPD) but not at the expense of worsening pain or dyspnoea (breathlessness)."
The data comes from a review of more than 30 studies looking at the health benefits of the exercise.
Past research has found that Tai Chi may reduce the risk of falls among older adults who are at increased risk.
What was that article about?

A:
Tai Chi is a suitable exercise for older people with conditions like arthritis, a study has found.