In the hours following the cessation of the siege in Sydney, there's been a number of people crawling out of the woodwork wondering why the police didn't bring in a sniper to shoot the hostage-taker and bring the thing to an early end. The plaints tend to go along the lines of "if a television camera can get a good shot, so can a sniper rifle; why didn't they get a sniper in?". Unfortunately, the police aren't allowed to respond to such asinine comments with the equivalent of a good solid clip around the ear, due to reasons of public relations and all. So I've decided to do it for them.
(If you're one of the people who has been making such remarks, please read the following very carefully, using the "speaking to the hard-of-thinking" voice in your head.)
1) A sniper rifle and a television camera look very different.
Googling the terms "image television camera" and "image sniper rifle" will bring up galleries of pictures of each of those. Each search takes about 0.3 of a second to complete. Given a hostage-taking gunman wants to cultivate the press, but discourage police snipers, it's likely even the most daft example of the breed in this day and age will probably try to familiarise themselves with the differences between the two - you could call it a necessary job skill. Seeing television cameras is a cue to pull out your list of demands and make it clear the hostages aren't dead yet. Seeing a sniper rifle is a cue to start really threatening the hostages. It's important not to muddle the two up.
2) A sniper rifle and a television camera have different fields of view.
Television cameras tend to work best at medium to close range. Sniper rifles are designed to work best at long range. So the position a television camera operator is occupying in order to obtain a decent shot (even through a zoom lens) is likely to be a lot closer than the position a sniper would need to be occupying in order to obtain a decent shot. Indeed, the television camera operator might well be blocking the field of view for the sniper.
3) Television cameras and sniper rifles are affected differently by weather conditions.
Television pictures tend not to be blown off course by strong or irregular winds. Sniper bullets, on the other hand, do. A television camera can get pictures in conditions where a sniper wouldn't be able to get a shot. Contrariwise, a sniper is capable of getting a shot off in conditions where the television camera is useless.
4) Real life is not like video games.
In video games, if your sniper misses a shot, you can always have another try, or go back to your last save point if you got killed. In real life, death is for keeps. In video games, the aim is usually to kill as many enemy combatants as possible, and never mind the collateral damage or the civilian casualties. In real life, the aim of the police in such situations is generally to try and keep the death count down - I have no doubt the NSW police were hoping to keep the death count in this particular case down to zero.
5) Real life is not like movies.
In the movies, snipers never miss the crucial shot. In real life, they can and do. In real life, the target of a sniper drops to the floor, dead, before they know they've been hit. In real life, even a bullet fired from a gun fitted with a noise suppressor is loud, and gives at least some warning. In the movies, accidents don't happen to disrupt that crucial shot - civilians don't walk into the path of a sniper's bullet at exactly the wrong moment, the target doesn't move, and the whole thing goes perfectly. In real life, accidents can and do happen. In the movies, there's always a crucial shot to take. In real life, there may not be.
Incidentally, the reason both movies and video games are so different from real life is because both of these media are constructed stories, following a set narrative which was created by humans to be culturally satisfying. Real life runs on different rails, and doesn't have to satisfy anyone.
6) At the time the most-used television shot was taken, the siege was barely begun.
The passing shots of the gunman in the cafe were taken very early on in the siege. They were the first visuals the wider public had of the situation. The fact they were widely circulated is actually a marker of how unusual they were - if there'd been more shots, we would have seen more pictures of the gunman. As it was, we got that one rather blurry image of the gunman, positioned behind his hostages, which was repeated regularly throughout the day. It wasn't replaced. It wasn't superseded by something new throughout the course of the sixteen hours of the siege. So it's likely that shot was the ONLY shot the television cameras got of the gunman (and once he realised television cameras could see him, he made damn certain he wasn't in view of them again, because he's just as capable of doing the "if the cameras can see me, so can a sniper" math as anyone else).
7) How do you know they didn't call a sniper in?
It seems highly likely to me that the NSW police (who strike me as a competent force on the whole) would have called in at least one sniper to get a look at things and see firstly whether there was a suitable vantage for them to be working from, and secondly, whether they were likely to get a decent shot at the gunman without risking the hostages. If a sniper wasn't used, it was probably because in the professional judgement of both the sniper(s) themselves, and of the person in charge of the operation, the risks of using a sniper outweighed the potential benefits.
Essentially, my point is this: the people who are wondering about the snipers, or wondering why things were done thus rather than so weren't there and weren't responsible for making the decisions. Things turned out poorly in one respect - three people died, and another eight were injured or treated in hospital. However, in another respect, things turned out surprisingly well - only three people died, one of whom was the gunman; the majority of the injured were mainly taken to hospital for observation and monitoring; and at least five of the hostages escaped completely unscathed. It could have been better, and it could have been much, much worse.
We in the general public cannot possibly wish to find out what went wrong more than the police do. We aren't the ones who will have to live with the knowledge we were supposed to save the lives of the three people who died, and yet we couldn't. The police on scene did the best job they could. The back-seat driving and "Monday's Expert" commentary from various members of the general public most definitely isn't helping. If you think you could have done better, go speak with your local police force, and offer them your expertise for the next time (gods forbid) this happens. Or, alternatively, go join your local police force yourself. Put your life on the line, put your precious skin at risk, and put your money where your damn-fool mouth is. Otherwise, shut the merry hells up and stop second-guessing the people who do this for a living.
PS: For those bitching about the fact the gunman was out on bail - that's a problem for the justice system, not the police force. For those whining about the way ASIO didn't spot this guy as a threat - I suspect they're looking for people who are going to group together to create terrorist cells and undertake complicated plots. This siege, while it had some of the trappings of terrorist activity (the calls for the IS flag etc) was actually something which has more in common with the sorts of "lone gunman" attacks which are so common in the USA, and was probably undertaken for similar reasons to those. Namely, one over-entitled man decided other people ought to die or be terrified in the service of boosting his ego.
EDITED TO ADD (19 DEC 2014): One other little wrinkle about why the NSW police might have decided a sniper was a Bad Move - it's an extra-judicial killing, or to put it in more blunt terms, deliberate murder. We don't have the death penalty here in Australia; if the police kill someone, there's usually an enquiry into the matter (which is, in fact, the process which is being started in NSW now) and charges can and will be laid against the officer responsible. It can be a career-limiting move.