The fact that making a false allegation of a crime may be an attempt to pervert the course of justice is well documented. Perhaps it should be obvious, but false submissions on a plea of mitigation can be as well.
In R v Bailey  2 Cr App R (S) 47;  EWCA Crim 136 the appellant was initially sentenced for three offences of indecent assault on a child.
Burton J [at 2]:
The applicant had set up an elaborate series of lies which enabled mitigation to be put forward to the court, which resulted in a three year community rehabilitation order being imposed, with a condition that he attended a Sex Offenders Group Work Programme. He told a psychiatrist, the probation officer, his solicitor and his counsel that he had had a relationship with a lady who was the mother of his child: she had been murdered, and the child had been killed by a speeding car within weeks of each other. This created a dramatic atmosphere of compassion on his behalf in relation to this extraordinary series of circumstances which he put forward as his excuse for having committed the offences, and accordingly the court was hoodwinked into imposing the three year community rehabilitation order. It subsequently came out that there was no truth whatever in the matter. The applicant had never had a partner or a child with any partner. Certainly there was no partner murdered and no child killed. Consequently he was charged with perverting the course of justice.
The appellant was sentenced to two and a half years imprisonment for the lies, and that penalty was upheld on appeal. It was probably more than he would have received for the original offending if he had provided true instructions.