A seemingly brilliant candidate emerges. That person is placed. And months or years later, it turns out that the brilliant candidate may have committed an act of terrorism. Who is responsible? It is time that we must come to grips with the sad truth that — in the event that person is guilty of committing that act — there is no foolproof way to determine if a person has the propensity to do harm. Assessment centres can help. So can rigorous checks of a candidate's background. Psychometric tests might go the furthest in being able to illuminate the presence of fanaticism. But "sleepers" —people, usually without criminal records, who live normal day-to-day lives as they await their call to action — are not a new phenomenon in this country. An inquiry into NHS recruitment practices seems a knee-jerk reaction to what is truly a question of mind reading and understanding the motivations behind human behaviour. See our lead news story on page 5.