yes so the liability can fall on you so its better to keep defence real and strong that on instruction of BM you issued to the customer himself on verification of ID further for back side of voucher you will need a defence as to how it was signed by third party.
Also departmental inquiry can be setup against you too,
further are you just called for witness or allegations are against you??
kindly specify you question you have narrated the facts but what advise do you need has to be specified.