  In this paper we study null Bertrand curves in $R_{1}^{4}$ under the
assumption the curve has a Cartan frame. We show that if the derivative vectors
of the null Cartan curve in $R_{1}^{4}$ is linearly independent, then this
curve is not a Bertrand curve. Since then the already known notion of null
Bertrand curves in $R_{1}^{4}$ occurs only if the derivative vectors of the
curve is linearly dependent. We will introduce an idea of Bertrand curves and
abiding by this idea we bring to light under which conditions a null Cartan
curve in $R_{1}^{4}$ is a Bertrand curve.
