A precise determination of the effective B0
s → K + K − lifetime can be used to constrain contributions from
physics beyond the Standard Model in the B0
s meson system. Conventional approaches select B meson
decay products that are significantly displaced from the B meson production vertex. As a consequence,
B mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which
must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural
network based trigger and event selection. Using 1.0 fb−1 of data recorded by the LHCb experiment, the
effective B0
s → K + K − lifetime is measured as 1.455 ± 0.046 (stat.) ± 0.006 (syst.) ps.