  We report results from a study of the spin and parity of $\Xi_{c}(2970)^+$
using a $980~\mathrm{fb^{-1}}$ data sample collected by the Belle detector at
the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The decay angle distributions
in the chain $\Xi_{c}(2970)^+ \to \Xi_c(2645)^{0}\pi^{+} \to
\Xi_c^{+}\pi^{-}\pi^{+}$ are analyzed to determine the spin of this
charmed-strange baryon. The angular distributions strongly favor the
$\Xi_{c}(2970)^+$ spin $J =1/2$ over $3/2$ or $5/2$, under an assumption that
the lowest partial wave dominates in the decay. We also measure the ratio of
$\Xi_{c}(2970)^+$ decay branching fractions $R={\mathcal{B}[ \Xi_{c}(2970)^+
\to \Xi_c(2645)^{0}\pi^{+} ]} / { \mathcal{B}[ \Xi_{c}(2970)^+ \to
\Xi_c^{\prime0}\pi^{+} ]} =1.67 \pm 0.29\mathrm{(stat.)}^{ +0.15}_{
-0.09}\mathrm{(syst.)} \pm 0.25\mathrm{(IS)}$, where the last uncertainty is
due to possible isospin-symmetry-breaking effects. This $R$ value favors the
spin-parity $J^P=1/2^+$ with the spin of the light-quark degrees of freedom
$s_{l}=0$. This is the first determination of the spin and parity of a
charmed-strange baryon.
