Elliptic Curve Point at Inifnity in Projective Coordinates
The curve equation for an elliptic curve in Jacobian form is

$$Y^2 = X^3 + aXZ^4+bZ^6.$$

If $Z=0$, then $Y^2=X^3$, and all points satisfying this are of the form $(\lambda^2 :\lambda^3:0)$, where $\lambda$ is in the finite field you are working over. Projectively, these are all equal to $(1 : 1 : 0)$, and therefore the only point on the curve satisfying $Z=0$ is $(1 : 1 : 0)$. This is why we refer to it as the point at infinity, and not a point at infinity (points with $Z=0$ can be thought of as lying at infinity). 

Assuming that your points are one the curve, it is therefore enough to check that $Z=0$.