The ruling in miranda v arizona most affected the procedure in which step of this process

The arrest of a criminal suspect.

If you've ever watched a television crime drama, you've heard the "Miranda warning" -- or at least the beginning of it:  "You have the right to remain silent. Anything you say can and will be used against you in a court of law. You have the right to an attorney "  There's a couple more sentences to the warning, but TV shows often cut to the next scene before hearing the arresting officer finish their recitation of the full warning.

Miranda v. Arizona was a Supreme Court case decided in 1966.  Ernesto Miranda was accused of kidnapping and raping a woman.  He confessed to the crime when interrogated by police, but attorneys argued that he did not fully understand his 6th Amendment rights.  After the decision in Miranda v. Arizona, it has become standard procedure in all arrests that the arresting officers must clearly state the accused person's rights -- their "Miranda rights," as they have become known.