  A linear CKM relation, $\bar\eta= \tan\Phi_{3/2}(\bar\rho-0.24\pm 0.03)$,
involving a $1\sigma$ range for $\Phi_{3/2}$, $20^\circ < \Phi_{3/2} <
115^\circ$, is obtained from $B^0\to K^*\pi$ amplitudes measured recently in
Dalitz plot analyses of $B^0\to K^+\pi^-\pi^0$ and $B^0(t)\to K_S\pi^+\pi^-$.
This relation is consistent within the large error on $\Phi_{3/2}$ with other
CKM constraints which are unaffected by new $b\to s\bar q q$ operators.
Sensitivity of the method to a new physics contribution in the $\Delta S=\Delta
I=1$ amplitude is discussed.
