If someone, especially in a court, is told something in mitigation, they are told something that makes a crime or fault easier to understand and excuse.
[formal]
Kieran Coonan QC told the judge in mitigation that the offences had been at the lowerend of the scale.
In mitigation, he points out that for his last decade his friend was ill.
See full dictionary entry for mitigation
Examples of 'in mitigation' in a sentence
in mitigation
`Geography,' he said, adding, `with Economics,' like a plea in mitigation.
Anthony Masters CASCADES - THE DAY OF THE DEAD (2001)