  There is a long-standing puzzle that the CP violation (CPV) in the baryon
systems has never been well established in experiments, while the CPV of mesons
have been observed by decades. In this paper, we propose that the CPV of baryon
decays can be generated by the scatterings of a nucleon and a pion into some
final states, i.e. $N\pi$ scatterings. Benefited by the fruitful data of $N\pi$
scatterings, we can model-independently analyse the strong phases of $b$-baryon
decays using the partial wave amplitudes of $N\pi$ scatterings. This makes a
great advantage to predict the CPV of baryon decays. We study the processes of
$\Lambda_b^0\to (p\pi^+\pi^-)h^-$, $(p\pi^0)h^-$ with $h=\pi$ or $K$. It is
found that the total CPV of the above processes in the invariant mass region of
$N\pi$ scatterings are at the order of several percent. More importantly, the
regional CPV in the Dalitz plot can reach as large as $20\%$. Therefore, we
suggest to measure the CPV of these processes, which has a large possibility to
achieve the first observation of CPV in the baryon system.
