Someone with severe disabilities that gets disability benefits
in the UK, DLA refers to Disability Living Allowance, which is availble to anyone who isn't quite normal
Case is used in the subjective "nutCASE" style undertone.
Pete) OMFG, look at that fucking tard, how'd he get a new car?
Tom) Yeah I know him from school, fucking DLA case - gets it free off social coz he's too fat to walk
Pete) Lets steal his fucking keys then, my tax paid for that shit ffs, all i got is a banger