The main characters occasionally speak English (?)

I found it odd that two of the main characters, S.I. Sanjay Shellar and AIG Satam, occasionally speak to each other in a mixture of what I assume to be Marathi (the official language of Mumbai) and English. Have some English words and phrases become part of the mainstream vocabulary of India? Or perhaps there are no 'local' expressions for what the characters were trying to say? Or might the insertion of a little English here and there be an allusion to the fact that many foreign countries still consider 'serial killers' to predominately be American and British 'afflictions'? Just wondering....