Do not commit injustice in rendering judgement.
“Do no injustice in judgement” Vayikra 19:15
This means not to declare the guilty innocent or the innocent guilty.
Included is the prohibition not to delay the verdict after it has become evident to the judge where justice lies.
If he deliberates extensively on clear matters to cause distress to one of the litigants- this is included in the category of injustice.