Wireless sensor networks (WSN) MAC protocol has been the active research area since last few years because of application specific nature of these networks. This paper studies popular contention based SMAC protocol in multihop scenario and analyzes its suitability in mission critical WSN applications. Along with the residual energy, the throughput and packet delivery ratio are considered as the important parameters for mission critical applications. Improvements are suggested in the SMAC protocol with the simulation results in NS-2. © 2013 IEEE.