  We present a pedagogical discussion on the time evolution of a Gaussian
neutrino wave packet in free space. A common treatment is to keep momentum
terms up to the quadratic order in the expansion of the energy-momentum
relation so that the Fourier transform can be evaluated analytically via
Gaussian integrals. This leads to a solution representing a flat Gaussian
distribution with a constant longitudinal width and a spreading transverse
width, which suggests that special relativity would be violated if the neutrino
wave packet were detected on its edge. However, we demonstrate that by
including terms of higher order in momentum the correct geometry of the wave
packet is restored. The corrected solution has a spherical wave front so that
it complies with special relativity.
