The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of p-shell Λ-hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for ⁷_ΛLi, ⁹_ΛBe, ¹¹_ΛB and ¹⁵_ΛN. The shape of the π⁻ spectra was interpreted through a comparison with pion distorted wave calculations that take into account the structure of both hypernucleus and daughter nucleus. Branching ratios [Formula: see text] were derived from the measured spectra and converted to π⁻ decay rates [Formula: see text] by means of known or extrapolated total decay widths Γ_tot of p-shell Λ-hypernuclei. Based on these measurements, the spin-parity assignment 1/2⁺ for ⁷_ΛLi and 5/2⁺ for ¹¹_ΛB ground-state are confirmed and a spin-parity 3/2⁺ for ¹⁵_ΛN ground-state is assigned for the first time.