While steps will be taken to deal with these lapses, they should be seen in perspective and there should not be a rush to over-simplistic answers, he said.

Responding to four MPs, he painted a picture of the complex security climate facing the Home Team.

'Perfection is the ideal to aim for. But imperfection is the reality we have to work with every day,' he said.

Three incidents - the escape of terrorist Mas Selamat Kastari, the attempted escape of criminal suspects from cells in the Subordinate Courts and a passport mix-up - have sparked questions over how secure the country is.

Mr Shanmugam said these were examples of 'episodic individual failure'.

'There has been failure to comply with SOP - we acknowledge that,' he told the House.

Audits were fine, but an audit 'cannot stop the individual officer opening a gate without looking at his screen, nor can it help to prevent an officer failing to check the passport against the boarding pass', he added.

When lapses do occur, he said, culprits would be confronted and dealt with.

The litigator-turned-minister also pointed out that the three lapses cannot be lumped together.

He cited the example of retiree Ang Heng Soon who managed to clear all security checks and board a flight to Vietnam using his son's passport.

Mr Shanmugam said the officer who dealt with Mr Ang had done many things right: He had assessed whether Mr Ang fit a terrorist profile, whether he was behaving suspiciously, and whether the passport had been tampered with or forged.

The mistake came when he assumed Mr Ang's failure to clear automated gates was due to a technical glitch.

'He will be penalised for that error. But we must also be fair to the officer in question. He exercised most of the security protocols correctly but made an error in not checking the passport against the boarding pass. To equate this case as the same as that of the Mas Selamat escape would be quite wrong,' said the minister.

With more than 140 million travellers passing through Singapore's checkpoints annually, it would be foolhardy to guarantee that there would not be a similar case in the future, he added.

To be completely security-sealed, he said, would suffocate business and freedom.

'It is a cure worse than the disease it is trying to prevent,' he said.

The real test of security must be whether there is a sense of safety, whether people can walk about freely, without fear, and whether the police force is trusted and generally free of corruption, he noted.

By these benchmarks, said Mr Shanmugam, the Home Team had done a good job.

So while the recent mistakes should be confronted and dealt with, this should be with 'a sense of balance and on an informed basis, understanding the context and the complexity of the issues involved', he said.

JEREMY AU YONG

WORKING WITH THE REALITY OF IMPERFECTION, REVIEW