Question:

A person died in an accident. A post-mortem examination was conducted on him. His body was then sent to his home three days later. His house was far and due to the delay a stench emanated from his corpse. Without bathing or shrouding his corpse he was buried after the janazah. Was the janazah prayer valid or not? How is ghusl made on a body on which a post-mortem was conducted since in such instances the limbs are usually separated?

Answer:  حامدا ومصليا ومسلما

One of the conditions of validity of the janazah prayer is the taharah (cleanliness and ritual purity) of the deceased. Janazah prayer is not valid on a person that was not bathed.

“وشرائطها” ستة … “والثاني طهارته” عن نجاسة حكمية وحقيقية في البدن فلا تصح على من لم يغسل.  (حاشية الطحطاوي على مراقي الفلاح)

Now, if due to ignorance or forgetfulness, a deceased was not bathed and the people performed the janazah prayer on him and buried him, then the janazah salah should be repeated on his grave provided that such a long time has not passed since burial in which a corpse would usually burst.

ولو صلي عليه بلا غسل جهلا أو نسيانا ثم دفن ولا يخرج إلا بالنبش أعيدت على قبره استحسانا لفساد الأولى. (ايضا 318)

“وإن دفن” وأهيل عليه التراب “بلا صلاة” … “صلى على قبره وإن لم يغسل” لسقوط شرط طهارته لحرمة نبشه  …”ما لم يتفسخ”. (ايضا 324)

In an autopsy the limbs of a body are not severed (usually), rather the corpse is cut opened and some organs are removed, then it is sewn up. In ghusl simply pouring water on the whole body is sufficient.

And Allah Ta’aalaa knows best
(Hazrat Mufti) Ahmed Khanpuri (May Allah preserve him)
Mahmoodul Fataawaa 1/543-544