Summary:

Rounding up familiar pawns means gathering a group of people and associating them with a crime, regardless of whether there is any evidence to support it. The mere instruction to round up criminals to arrest, even though he knew who the real perpetrator was, highlights the bureaucratic circumstances at the time.

https://www.youtube.com/watch?v=_ss8kaYq-n8

A similar phrase was also used in "Blazing Saddles," where a group of evil men is rounded up to carry out the government's vicious actions.

https://www.youtube.com/watch?v=fLpmswBKVN4

Times have not changed because the same occurs today when the government pursues and prosecutes political prisoners for their oppositional views. The phrase has become common to describe the targeting of familiar individuals for investigation as a form of political retribution or payback for hostilities between the government and the people.

Estimates vary, but 5-6% of individuals currently incarcerated in the U.S. may be wrongfully convicted and not guilty of the crime.

https://www.georgiainnocenceproject.org/general/beneath-the-statistics-the-structural-and-systemic-causes-of-our-wrongful-conviction-problem/

To Kill A Mockingbird, closing arguments by Atticus Finch, Attorney:

https://www.youtube.com/watch?v=tNxrnOC_WTs