[en] It is empirically observed that the non-leptonic decay of strange hadrons is enhanced when the change in isospin is 1/2. This is generalized in the ''ΔI = 1/2 rule'' that states that all such decays proceed predominantly through ΔI = 1/2 amplitudes. However, there is no definitive explanation for this apparently universal rule. Non-mesonic decay of Λ-hypernuclei can occur through a weak decay process ΛN -> ηN. When stimulated by a neutron, two neutrons are emitted from the nucleus, and when stimulated by a proton, a proton and neutron are emitted. By measuring the relative decay widths (Γ_n/Γ_p) in the full set of s-shell hypernuclei, a sensitive test of the ΔI = 1/2 rule, and the determination of its applicability to non-mesonic decays can be made. In addition, information about the spin-isospin dependence of the weak decay process can be extracted. A measurement of Γ_n/Γ_p, to an accuracy of even 50% will be sufficient to address important issues relating to the ΔI = 1/2 rule and to the weak decay process. The experiment will measure the ratio Γ_n/Γ_p, following the decay of ⁴H which is produced by a stopped K^- beam in a liquid Helium target. The Neutral Meson Spectrometer will be used to identify stopped kaon events by detection of the gamma rays that follow the decay of the emitted π⁰. Arrays of charged particle and neutron detectors will measure the relative neutron and proton emission probabilities. An engineering run was performed in 1998, without the Helium target, which demonstrated that the technique is feasible. The full experiment is scheduled at the Alternating Gradient Synchrotron for the spring 2001 running period