What is a litigant and mitigant?

No, they are not synonymous.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 3 words with the pattern -I--GAN-. That is, eight letter words with 2nd letter I and 5th letter G and 6th letter A and 7th letter N. In alphabetical order, they are: hiragana litigant mitigant

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 4 words with the pattern -ITIG---. That is, eight letter words with 2nd letter I and 3rd letter T and 4th letter I and 5th letter G. In alphabetical order, they are: litigant litigate mitigant mitigate

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 6 words with the pattern ---IGAN-. That is, eight letter words with 4th letter I and 5th letter G and 6th letter A and 7th letter N. In alphabetical order, they are: antigang fumigant litigant mitigant obligant wanigans

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern --T-GA-T. That is, eight letter words with 3rd letter T and 5th letter G and 6th letter A and 8th letter T. In alphabetical order, they are: litigant mitigant

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern -ITI-A-T. That is, eight letter words with 2nd letter I and 3rd letter T and 4th letter I and 6th letter A and 8th letter T. In alphabetical order, they are: litigant mitigant

No the term litigant applies almost exclusively to civil law or tort cases. The individual accused of a crime is known as the defendant.