  We derive the expression for the jerk parameter in $f(R)$ gravity. We use the
Palatini variational principle and the field equations in the Einstein
conformal gauge. For the particular case $f(R)=R-\frac{\alpha^2}{3R}$, the
predicted value of the jerk parameter agrees with the SNLS SNIa and X-ray
galaxy cluster distance data but does not with the SNIa gold sample data.
