A guard etch is a much cleaner solution to the same problem. A guard is a piece of etch which surrounds the sensitive node on both sides of the board, and shunts away any leakage currents. The guard must connect to a low impedance point which is at the same voltage as the node it is protecting. Ideally, the guard should surround the node completely. Ask the engineer if there are any points that need to be guarded, and how to drive the guards.
Ground planes have a similar shunting effect on capacitively coupled noise.
They are most effective if placed directly between the source and the sensitive node. Separate sheets of metal have the same effect, and also will block radio waves and high frequency magnetic fields. Magnetic fields are hard to shield below about 10 kHz. Shields are most effective when they completely enclose the sensitive circuit. Wires can carry noise in and out of a system, but adding the right filters will stop it.