Playing the statistics game with Ken Clarke.
Not in dispute is that Clarke was right to say that 75% of those over 18 who have been charged with an offence connected with the riots had received a previous caution or conviction. In fact, the actual figure is 77%, and the overall figure, including juveniles is 73% (page 5). Where it gets more interesting and informative is when you drill down further into the figures: unconnected with the riots entirely is that 28% of males aged 18-52, or more than 1 in 4, has at least a caution on their record. Also likely to be used as grist to the "feral underclass" mill is that 40% of the male juveniles charged with an offence following the disorder had committed at least one previous offence, compared with just 2% of the 10-17 male population as a whole.
So far then it does look as though the "criminal classes" were mainly those running amok. Other comparative data provided however blunts this somewhat: the 27% so far charged who didn't have a previous record is in fact a higher percentage than the 23% who found themselves up before the beak for the first time last year. Similarly, this data is meaningless without knowing the severity of the past crimes committed: 38.7% were summary and breach offences, while 23.5% were theft and handling stolen goods, the majority of which are likely to be shoplifting. The more serious burglary, robbery and violence against the person make up 4.7%, 3.6% and 6.0% respectively (Table 18, page 23). 9.6% of the 16,598 offences (1,586) were dealt with using cautions, suggesting those committing them were first or second time offenders. Crucially though, we don't yet know (and probably never will) just how long ago these previous offences were committed: the courts, as evidenced by Judge Chapple (PDF), usually ignore previous one-off minor brushes with the law when they took place over 5 years ago when passing sentence. That 28% of males between 18 and 52 have a record of some sort doesn't automatically make them a "criminal"; the same equally applies with the 77% charged so far.
We additionally have to take into account that a distinct percentage of the 1,715 who have so far passed through the courts charged in connection with the riots could be described as "low-hanging fruit": those already well known to the police and whom were identified by officers at the time and picked up afterwards, or later spotted on CCTV; those with records who left behind fingerprints; and those who have a "reputation", who suddenly came into possession of electrical goods and clothing at the same time as the disturbances and were duly grassed up. They were, as Paul and Reuben both point out, far easier to catch than those completely unknown to the police. The Ministry of Justice promises a further publication at the end of October covering wider "socio-economic and demographic characteristics" of those involved. Politicians and commentators alike would do well to wait at least until then before claiming any sort of vindication.