We make use of the phase space density approach to discuss gravitino as a warm dark matter candidate .
Barring fine tuning between the reheat temperature in the Universe and superparticle masses , we find that warm gravitinos have both appropriate total mass density , \Omega _ { \tilde { G } } = \Omega _ { DM } \simeq 0.2 , and suitable primordial phase space density at low momenta provided that their mass is in the range 1 \text { keV } \lesssim m _ { \tilde { G } } \lesssim 15 ~ { } \text { keV } , the reheat temperature in the Universe is low , T _ { R } \lesssim 10 ~ { } \mbox { TeV } , and masses of some of the superparticles are sufficiently small , M \lesssim 350 ~ { } \mbox { GeV } .
The latter property implies that the gravitino warm dark matter scenario will be either ruled out or supported by the LHC experiments .