They turned him in to the police.
They turned him over to the police.
Are they exactly the same in meaning?
According to the Cambridge Dictionary, Turn somebody in means taking a criminal to the police. In my opinion, it can also mean telling the police where the criminal is, so that they can arrest them. Collins Dictionary agrees with me on this.
This expression is often used reflexively:
The driver turned himself in two days after the accident
According to Merriam Webster (US) it can also mean to betray somebody, i.e. tell the police who committed a crime. I don't think that it has this meaning in the UK, though there is an informal expression dob somebody in which means to secretly tell the police that somebody has committed a crime.
To turn somebody over to the police means "take a criminal to the police or other authority"