Optical Kerr gating technique has been employed to investigate the life history of relativistic electrons in solids by temporally gating their Cherenkov emission. Mega-ampere currents of relativistic electrons are created during ultra-intense (2 × 1019 W/cm2) laser-solid interactions. In order to measure the lifetime of these relativistic electrons in solids, we temporally gate their Cherenkov emission using an optical Kerr gate (OKG). The OKG is induced in a nonlinear medium, namely, carbon-di-sulphide (CS2), with a measured gate-width (FWHM) of 2 ps. The gate femtosecond laser pulse is synchronized with the intense interaction pulse generating relativistic electrons. The arrival time of the gate laser pulse on the CS2 cell is varied with the help of a delay stage. We find that Cherenkov emission from relativistic electrons created with a ultra-short laser pulse (25 fs) lives as long as 120 ps, a few thousand times that of the incident light pulse.