This paper describes the angular distribution of ${\Lambda }_b^0\to \Lambda \left(\to p{K}^{-}\right){\ell }^{+}{\ell }^{-}$ $$ {\Lambda}_b^0\to \Lambda \left(\to p{K}^{-}\right){\ell}^{+}{\ell}^{-} $$ decays. A full expression is given for the case of multiple interfering spin-states with spin ≤ $\frac{5}{2}$ $$ \frac{5}{2} $$ . This distribution is relevant for future measurements of ${\Lambda }_b^0\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ $$ {\Lambda}_b^0\to p{K}^{-}{\ell}^{+}{\ell}^{-} $$ decays, where different states cannot easily be separated based on their mass alone. New observables arise when considering spin- $\frac{5}{2}$ $$ \frac{5}{2} $$ states as well as interference between states. An exploration of their behaviour for a variety of beyond the Standard Model scenarios shows that some of these observables exhibit interesting sensitivity to the Wilson coefficients involved in b → sℓ + ℓ − transitions. Others are insensitive to the Wilson coefficients and can be used to verify the description of ${\Lambda }_b^0\to \Lambda$ $$ {\Lambda}_b^0\to \Lambda $$ form-factors. A basis of weighting functions that can be used to determine all of the angular observables described in this paper in a moment analysis of the experimental data is also provided.