  We theoretically investigate the charge noise and dephasing in a metallic
device in close proximity to a spin incoherent Luttinger liquid with a small
but finite current. The frequency dependence of the charge noise exhibits a
loss of frequency peaks corresponding to the $2k_F$ part of the density
correlations in the electron liquid when the temperature $T$ is increased from
values below the magnetic exchange energy $J$ of the electron gas to values
above it. The dephasing rate in a nearby metallic nanostructure also shows a
cross-over for $T \sim J$ and may exhibit a non-monotonic temperature
dependence. For a range of temperatures the dephasing rate {\em decreases} with
increasing temperatures. The proposed experiments provide a convenient approach
to probe the spin-incoherent Luttinger liquid and should be implementable in a
wide variety of systems.
