  We critically study the possibility of quantum Zeno effect for indirect
measurements. If the detector is prepared to detect the emitted signal from the
core system, and the detector does not reflect the signal back to the core
system, then we can prove the decay probability of the system is not changed by
the continuous measurement of the signal and the quantum Zeno effect never
takes place. This argument also applies to the quantum Zeno effect for
accelerated two-level systems, unstable particle decay, etc.
