Answer:
This has many problems. First, the police has to read him the Miranda rights. Second, he has a right to a lawyer as a American Citizen (I assume this is in America). Third, pressure to confess is not legal, if he had a lawyer this would be known.
Step-by-step explanation:
Without being read his rights, when the case goes to trial, the attorney against John cannot use anything he says, "You have the right to remain silent, anything you say can, and will be used aganist you". It more of impacts the trial than John, and it could possably affect the whole trial. In America, anyone arrested is allowed to have a lawyer present, "You can have a lawyer present, if you cannot afford one, one will be provided for you."