Is hindsight always a benefit in law?
Hindsight's a wonderful thing.
How often have you heard that phrase?
There is probably an event in our lives every week when, with the benefit of hindsight - the wisdom that comes from viewing actions after seeing the consequences - we think we shouldn't have done that or should have done it this way instead.
The drink after work that means you miss the train; the text sent in anger that causes an even bigger upset; the short-cut that turns into a dead end.
It's an entirely human reaction that we should look back at our decisions when they go wrong and say: "If only."
But when it comes to life-changing incidents, is 20:20 vision after the event a fair way for official bodies to assess where fault lies?
Has that process of re-examination gone too far? Or is it the only way we learn lessons for the future?
These are issues that have concerned me over many years covering court cases, inquests and inquiries in which prison officers, police and security staff have had to defend and explain their actions.
The bereaved rightly demand answers as to how their loved ones have died and the public has a right to know if someone has been killed because of neglect, misconduct or a deliberate, and illegal, act.
But in some cases, particularly those of fatal shootings by police, decisions are scrutinised in the most extraordinary detail.
Months, sometimes years, after a firearms incident, barristers will question an officer, their colleagues and witnesses about those few seconds, fractions of seconds even, when the judgment was made to pull the trigger.
Those questions take place in the clinical setting of a courtroom, far removed from the pressure-laden environment in which that decision was made.
Here is an extract from the five-hour questioning of the policeman who killed Mark Duggan, in Tottenham, north London, in August 2011 - the shooting which sparked riots in London that spread to other cities in England in the worst disorder for a generation.
The officer, known only as V53, was being cross-examined by Leslie Thomas QC, for Mr Duggan's family, at the inquest into his death, two years on from the incident, and after V53 had given evidence at two linked criminal trials.
V53 fired two shots at Mark Duggan in rapid succession. He was asked whether, based on reconstructive modelling that had been done, his account of which shot had been fired first was accurate:
Thomas: Not only do you have the angle, the chest shot with the angle going downwards, but it's also going from right to left, do you follow?
V53: Yes, I do follow, sir, yes.
Thomas: Which would suggest that when Mark Duggan was shot in the chest, he was at an angle facing towards where the minicab is. He would have been facing towards the minicab; do you follow?
V53: Sorry, sir, I appreciate your movements but whereabouts are you saying Mark Duggan would have been standing, with his back to the minicab?
Thomas: You are standing where you are standing - imagine you are you, Mark Duggan is in front of you, the minicab would be to the left of Mark Duggan, to your right?
Thomas: What I'm saying is, for the bullet to have entered the right-hand side and to have slightly come out on the left-hand side he would have had to have been tilted towards the minicab; do you follow?
V53: I do follow, yes, sir.
Thomas: That's not what you say happened, is it?
V53: No, sir, it's not.
Thomas: You see, I'm going to suggest the science doesn't support your account at all.
At the end of the 13-week inquest, the jury concluded that Mark Duggan had been "lawfully killed".
John Tully, chairman of the Metropolitan Police Federation, said at the time: "Firearms officers are armed and trained to deal with the most serious threat to our society from criminals.
"They often have to make split-second decisions in order to protect themselves or the public in difficult circumstances.
"Their decisions are then scrutinised during a court processes (sic) which looks at the situation with the luxury of hindsight."
For some, though, it is not a luxury - it's a necessity: the only way to understand where mistakes have been made, hold people to account and ensure poor practice is changed.
Deborah Coles, co-director of Inquest, a charity that supports the families of those who have died in custody, including the Duggan family, says hindsight helps facilitate the rigorous probing of the actions of people whose duty it is to keep us safe.
"It's fundamental: if you don't look back, how can you move forward?" she says.
"These individuals have to be accountable for their conduct and you sign up to it when you take on that role."
According to Ms Coles, the problem with using hindsight arises when investigations into deaths at the hands of the state aren't put into the wider social and political context of resources and work pressures. The findings shouldn't be "isolated from the reality of the environment in which people are working", she says.
For Mike Tongue, the former Chief Constable of Gwent Police, the danger of hindsight comes with examining decisions in very old cases, when policing standards, attitudes and training were different to the present day, though he believes the reviewing bodies generally get the balance right.
He acknowledges, however, the strain that interrogation can put on officers who make "life and death decisions".
"It is difficult for firearm officers. They know their decisions will be pored over and reviewed.
"I feel sympathy for these people, when people are put under very, very stressful circumstances."
But Mr Tongue, who was once the policing lead in England and Wales on firearms and public order, believes hindsight has enabled important improvements to be made in police procedures, for example the use by officers of potentially dangerous techniques to restrain suspects.
In the absence of an alternative, hindsight remains the main tool for reviewing critical incidents - but we shouldn't forget that it has its imperfections.