Why Should David Chaytor Get A Lighter Sentence?

Widely reported this morning is the fact that we will see the first MP sentenced for his taxpayer-money-grubbing ways.

He faces a maximum of seven years in jail, although his guilty plea will be taken into account by the sentencing judge.
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He had denied the charges but appeared at the Old Bailey in December to change his plea, having failed in a court bid to argue that expenses cases should be heard by Parliament, not the courts.

Now, as Guido points out anything less than a custodial sentence should have baying mobs (rightly) calling for Mr. Justice Saunders head on a pike, but why should it be a short custodial sentence?

Having failed to get his case insulated from prosecution by parliamentary privilege, all the while claiming "accounting errors, nothing to see her etc.", Mr. Chaytor went on to plead guilty when it was fast apparent he wasn't above the law.

Almost makes you wonder if the BBC knows something we don't about the case and is preparing us for the narrative.