Longest possible detection of alcohol in the body ?

I got a D.U.I approximately 3 years ago. I still have to complete my counseling in order to receive my license back. They do drug test and there is supposedly a type of drug test that can detect alcohol even after a week. Is this true ?. Is it even possible to detect alcohol after that amount of time ?. I was under the umption a good 12 hrs. was more than enough. ?