US President Barack Obama could reveal his plans to cut gun violence later today, as New York becomes the first state to pass tough new laws on firearms.

Calls for tighter gun controls have been mounting in response to last month’s shooting at Sandy Hook Elementary School in Newtown, Connecticut, where gunman Adam Lanza shot dead 20 children and six adults.

But America’s powerful pro-gun lobby says it will resist attempts to undermine what it says is the constitutional right to bear arms.

Talk-show host Piers Morgan is leading calls for a ban on semi-automatic weapons, which were used in the Newtown massacre and in many other recent mass shootings.

Is Piers right?

Love him or hate him, the former Mirror editor is at the centre of much of the debate about gun control at the moment.

Piers has been fact-checked to death by various US news sources over his repeated claims that there were 11,000 gun murders in America last year and only 35 in Britain.

But he could be right about shootings in America, depending on which set of statistics you prefer to use.

There were 11,078 firearms homicides in 2010, according to the Center for Disease Control and Prevention.

The FBI puts the figure for that year much lower at 8,874 – a number which has been seized on by Piers’s critics – but the bureau’s records depend on voluntary contributions and may not be as comprehensive.

As far as the “35 gun murders in Britain” line goes, Piers has got this wrong. The Home Office recorded 60 shooting homicides in England and Wales in 2010/11. The average is 62 a year over the last 15 years.

Allow for population difference and we get a gun murder rate of about 0.1 per 100,000 people in England and Wales.

In America the rate is about 3.6 per 100,000 or about 2.9 per 100,000 if you prefer to use the FBI figures. The gun murder rate is 33 or 27 times higher in America, depending on where you get your data.

So Piers has made an error, but it doesn’t destroy the thrust of his argument.

Is America safer than Britain?

Critics have seized on the supposed fact that overall crime, and violent crime in particular, is apparently higher in Britain than in America.

The logic of this, presumably, is that the kind of tight gun laws that came in over here after the 1996 Dunblane tragedy haven’t made the country safer in general.

Much of the commentary on this appears to have been inspired by this 2009 report in the Mail, which quoted statistics circulated by the Conservative Party, then in opposition.

The article claimed that there were 2,034 violent incidents per 100,000 people in the UK and only 466 in America, a “fact” repeated endlessly on the internet in recent days. But the comparison is a meaningless one.

Some crimes are easy to compare on a country-by-country basis. Murders are fairly easy to count – you’re either dead or alive.

But what other incidents count as “violent crime”? Different countries will have different opinions about this, and the percentage of crimes that are actually reported to the police will vary wildly too, making international comparisons difficult.

The FBI – the source of that “466 in 100,000″ figure (the number is actually from 2007) – defines violent crime as murder, manslaughter, rape, robbery, and aggravated assault.

The British definition is much looser, including all crimes against the person and sexual offences, hence the much higher number.

And lumping all these various crimes together to get a total of “violent incidents” means that a murder and an assault count as one incident, making no allowance for the difference in seriousness.

So the article asks us to believe that Britain is more violent than South Africa, when nearly 17,000 people were murdered in South Africa in 2009 compared to fewer than 800 people here.

For what it’s worth, the United Nations Office on Drugs and Crime has had a stab at producing comparable crime stats for different parts of the world.

The latest figures suggest that the burglary rate in England and Wales is about 35 per cent higher and there are more than double the number of assaults per 100,000 residents.

Your chances of being robbed are about 20 per cent higher in England and Wales than in the US. But the figures for rape are almost identical, and you are massively more likely to be murdered in America, whether a gun is involved or not. The overall homicide rate is about four times higher.

More guns, more crime?

Not necessarily.

It’s true that America tops the Small Arms Survey’s world chart for gun ownership, with 88.8 guns per 100 residents. And the firearm murder rate is higher than in any other country in the developed world.

That’s a correlation, but it doesn’t prove causation. And this is a problem that dogs most attempts to infer definite conclusions from any of the many statistics on guns.

It’s equally true to say that Britain’s tighter gun laws didn’t lead to a significant drop in gun crime. And that the US gun murder rate is falling, even as gun ownership rises. But again, this doesn’t prove cause and effect.

We don’t know what would have happened if things had been different and we don’t know how far other factors are affecting crime.

Perhaps there would have been an explosion of gun crime here in the absence of the Dunblane laws. Maybe the rise in America’s prison population has led to a drop in violence on the streets and gun ownership has nothing to do with it.

This is why most major academic studies in the US have come to the same conclusion: that there isn’t enough evidence to say one way or the other that gun control laws will lead to fewer deaths.

The gun control debate will rage on in the US, but it’s unlikely that either side will be able to prove their case with statistics alone.

Why do Americans think they have the right to carry guns?

The second amendment to the US constitution, adopted in 1791, states: “A well regulated Militia, being necessary to the security of a free State, the Right of the People to keep and bear Arms, shall not be infringed.”

Gun lobbyists tend to focus on the second half of this sentence, rather than attempting to explain how the millions of individuals who own guns in the US constitute “a well regulated Militia”.

While trying to get into the heads of the men who wrote the Bill of Rights in the late 18th century might seem like an odd thing to do, that’s exactly what the US courts have to do when they rule on changes to gun laws.

When the second amendment was written, the big fear was that a federal US government backed by a standing army might become too powerful, and start to trample the rights of individual states.

Many of the founding fathers of the country thought the best defence against the kind of “tyrannical government” that still held sway in Europe was the widespread availability of weapons among civilian, who could band together to defend themselves from an oppressive government.

But what George Washington, Thomas Jefferson and the others had in mind by a “well regulated Militia” is up for debate. Did they really envisage private citizens building personal armouries at home?

In 1939 the Supreme Court said the second amendment did not guarantee the individual householder’s right to own whatever guns they liked outside the context of a militia.

The court only changed its mind in 2010 when it ruled in the case of that the US constitution could now be used to prevent states from banning handguns.

The ruling was passed by the narrowest of margins – five votes to four – with the four dissenting judges calling the majority decision a “dramatic upheaval in the law”.

So the idea that the US bill of rights has always given individual citizens the inalienable right to own whatever weapons they like is untrue. This is a highly controversial interpretation of the constitution and has only been good law for the last few years.

On the other hand, it’s equally clear that the right to bear arms wasn’t just about defending yourself, protecting your property from burglars, or even seeing off British redcoats.

It was specifically designed to give the general population the ability to fight an enemy within.

Thomas Jefferson said: “The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.”

And James Madison, the main author of the US constitution, wrote: “The governments of Europe are afraid to trust the people with arms. If they did, the people would surely shake off the yoke of tyranny.”

So when conservative commentators like Ben Shapiro talk about armed resistance to tyrannical government, this may sound to non-American ears like the stuff of extremist conspiracy theory, but it is entirely in keeping with the historical context of the US constitution.

By Patrick Worrall