Letter supporting Visa application

[Mailme2015]

My father's visitors visa had been rejected 3 times from Chennai consulate. Twice rejected for my parents when attended together. 3rd time my mom and dad went separately with 6 months gap in between. My mom was granted visa but not my dad. My dad's last attempt was in Jan '08. This time he is all set to try again in Hyd consulate in May.

My dad works for Anti Corruption Bureau for AP state government. My question is will a letter from his Director General(DG) stating that he will definitely return after his 4 months of stay since he had 14 months of service to complete will help him in getting Visa.

Thanks in advance. I really appreciate your response.

[Mailme2015]

I want to make sure the letter from his DG will not negatively impact the decision.

Thank you.