Of course, the fear of criminal immigrants doing bad deeds has another, simpler answer than mass deportation and the conflation of civil and criminal law, which is...
Standard, everyday police work in criminal investigation.
Huh? That's right: the best and most direct way to focus on and detain/incarcerate/deport criminal elements is by going after criminals using police work. Astounding notion!!! What a vast saving of time and resources compared to mass deportation, with the bonus that far fewer mistakes are made, and those we'd welcome to stay remain unmolested! Efficient, lawful, and respectful. How nice!
After all, as case after case after case shows, business, especially the construction, hospitality, health care and farming industries, need these human resources and cannot optimally function without them. Ditto the rotting strawberry patches in the UK, etc.
And that is the second tip: If migrant workers without papers are found, and you are so concerned, go to the domestic source of the problem over which you have full control: blame the employer and "string him up". Know why this is not the case? Ahem, I'm sure you do.