Police at the scene made the decision to shoot

The 31-year-old woman was shot after brandishing a gun outside a remote cottage on Saturday evening.

Firearms expert Mike Yardley called for a review of guidelines for armed police responding to firearms incidents after claims that the woman was carrying a "soft air pistol".

However, Professor Doug Sharp, a former West Midlands Police chief superintendent, said it was impossible to tell the difference between a replica weapon and a lethal firearm in a stand-off situation.

An armed response team from Lothian and Borders Police was called to the cottage near the hamlet of Colzium, about 15 miles south west of Edinburgh, after the woman telephoned to tell them she had shot her mother.

Police said the woman - known as Jenny and thought to be from London - was shot in the stomach after repeated requests to drop the weapon.

Staff at Edinburgh Royal Infirmary said the woman was in a "comfortable" condition, after undergoing surgery.

A police officer can only fire if he or she reasonably believes that his life or the life of an innocent bystander or any other person is immediately under threat Prof Doug Sharp Former chief superintendent

An investigation team from neighbouring Strathclyde Police, led by assistant chief constable Ricky Gray, is carrying out an inquiry into the shooting.

One theory being investigated by police is that the woman may have wanted to commit suicide, after a note was discovered - a so-called "suicide-by-cop".

Mr Yardley said the "shoot to stop" policy had resulted in a number of fatal incidents with people carrying items such as cigarette lighters or a table leg.

He said: "There are a range of options open to the police to prevent incidents like these.

"If they were armed with the right sort of weapons such as a carbine with optical sights they could shoot to wound. They could use Tasers or baton rounds or pepper spray.

"It's time we opened up a national debate on whether in certain circumstances it's appropriate to shoot to wound."

Firearms officer's decision

Professor Sharp, who dealt with numerous sieges during his time with West Midlands Police, said that the decision to shoot was always that of the officer at the scene with the firearm.

He said: "It is only the officer who is there, who knows exactly the circumstances, and the person who is ultimately responsible to the law, who has the decision.

"The person in command has no authority whatsoever to order someone to fire.

"I defy you to tell which is which"

"A police officer can only fire if he or she reasonably believes that his life or the life of an innocent bystander or any other person is immediately under threat.

"You are shooting to stop the threat which effectively means you are shooting at the torso, you are shooting to disable the person immediately and to make sure they cannot possible fire the weapon or they can't continue the threat."

The consequences of that are that you are effectively shooting to kill, he added.

'Plastic model'

Earlier this year, Lothian and Borders Police Deputy Chief Constable Tom Wood said it was impossible to tell the difference between a real and fake weapon.

He said: "I've got two weapons here in my hands and both of them look identical - even from three feet away.

"One is a real weapon, a deadly automatic pistol and the other is a cheap, plastic model worth about five pounds.

"I defy you to tell which is which."

He said he was concerned that one day a police officer would be forced to shoot someone who was carrying an imitation weapon.