islamic aqeedah (belief) is that Muhammad may peace be upon him,
is the last and final messenger of Allah.
so surely for your food to be halal the person who slaughters it must believe in this islamic aqeedah (belief) correct?
i also think you should check this link out,
it could answer any other questions you have about halal food,
Its basically a Halal Monitoring Committee,
they are run by various Ulama (Muslim Scholars),
located in leicester,
it has a lot of information and is very beneficial.
remember me in your duas :D