Should the person who has been killed wrongfully, like the shaheed, not  be washed or prayed for, or should he be washed and prayed for (janaazah or funeral prayer)?

Praise be to Allaah. 

The person who has been killed wrongfully should be washed
and prayed for. ‘Umar al-Faarooq (may Allaah be pleased with him) was
killed wrongfully, as was ‘Uthmaan ibn ‘Affaan (may Allaah be pleased
with him), but they were both washed and the Sahaabah (may Allaah be
pleased with them) prayed for them. ‘Ali was also killed wrongfully
but he was washed and prayed for.