Can one please confirm who the witnesses are? That they must have upstanding and integretity is my understanding. My husband has used his eldest who smokes illegal substances and on the 3rd that I have just received witnessed by a hindu?
If you ask about 'Gawahi' then It is acceptable of two Male trustworthy Muslims (naik and saleh) or one male and two females. And choosing Muslims for 'Gawahi' is preferred.
Tafheem ul Quran (Urdu)
The consensus of the Jumhoor is: Having witnesses is NOT required for divorce, although it's preferred (Mustahab) according to the second verse of Surat At-Talaq
And when they have [nearly] fulfilled their term, either retain them according to acceptable terms or part with them according to acceptable terms. And bring to witness two just men from among you and establish the testimony for [the acceptance of] Allah . That is instructed to whoever should believe in Allah and the Last day. And whoever fears Allah - He will make for him a way out
So in your case, having a witness who was a smoker or not would not make any difference and the divorce is still valid.
Allah knows best.