Ranb asked if any defendant "had used Holocaust denial" in their defense. That means did any defendants use the techniques of Holocaust deniers or do things like deny the existence of gas chambers. The answer is mostly no.
A war crimes trial defendant can deny they were there, deny knowledge, deny personal involvement, deny responsibility (plead superior orders), but can also try to minimise the crime. Which many did over the years - "yes there were some shootings but no they were just legitimate small-scale reprisals not full-blooded genocidal massacres".
These techniques are not really Holocaust denial, just typical defense strategies. Thus there was little call for denial in most trials. The only exception I know is where defense lawyers brought in an actual Holocaust denier into a shootings trial. That certainly counts as "using Holocaust denial", and was a failed desperation move that did not work, much as the defense lawyer who tried claiming that the killing of Jews was legal because Hitler said so and thus there was no legal basis for a prosecution of a legitimate act, failed to get his clients acquitted.
Defendants serving in extermination camps could do most of the above if they wanted, but also had the option to deny there were gas chambers at all. That would meet most people's definitions of Holocaust denial, which has really been gas chamber denial for more than 50 years But essentially none ever have.