CRISPR has revolutionized genetic engineering by providing straightforward tools for many kinds of genetic alterations. CRISPR-Cas13 is a programmable endonuclease that specifically targets and cleaves RNA. After activation by target cis-RNA binding, Cas13 also exhibits non-specific collateral trans-activity against nearby RNAs. In several conditions, this leads to apoptosis. Here, we propose to harness the collateral activity of RfxCas13d for selective induction of apoptosis in heterogeneous cell populations. We design and perform machine-guided engineering of RfxCas13d to increase collateral activity, with applications in highly specific cancer therapeutics.