Is it sufficient for the Mudarib to obtain a promissory note (sanad li-amr) from the buyer to absolve him of the responsibility for dereliction of duty (mas'uliyat al-tafrit) in the case of a consignment sale (al-bay' 'ala al-tasrif)?

No, it is not sufficient for the Mudarib to obtain a promissory note (sanad li-amr) from the buyer to absolve him of the responsibility for dereliction of duty (mas'uliyat al-tafrit) if the consignment sale (al-bay' 'ala al-tasrif) was conducted without the permission of the capital provider (rabb al-mal) and it is proven that it was not in the interest of the partnership (sharakah), because the dereliction of duty lies in the fundamental method of sale itself.