Helping cops in GTA San Andreas gets you a WANTED LEVEL — the exact opposite of Vice City!

In GTA Vice City, helping police arrest criminals earned you a 'Good Citizen Bonus.' But in San Andreas, if you try the same thing, you'll likely get a wanted level instead — apparently Rockstar decided it's 'interfering with police affairs.' You can still help secretly by blocking the criminal's car or killing them when cops aren't looking.

Source: Street Criminals (GTA SA) — CC BY-SA