We propose a physically motivated replacement for the speculative factors fl × fi in the Drake Equation. The Triple Lock Index (TLI) evaluates the probability ofcomplex (eukaryotic) life through three sequential filters: spectral compatibility with oxygenic photosynthesis (Filter 1), a sustained phosphorus cycle via plate tectonics(Filter 2), and an oceanic habitable zone permitting eukaryogenesis under stellar radiation (Filter 3). Applied to a catalogue of 13 worlds, TLI spans five orders ofmagnitude—from ∼5% (Kepler-442b) to 1%—all located beyond 140 light-years. This result exposes a systematic observational selection bias: current surveyspreferentially discover M-dwarf planets with low TLI, while physically promising K-and G-dwarf candidates remain underrepresented.