Non-repudiation is one of the challenges in smart grids. A malicious smart meter is capable of compromising the power readings without being detected since it may be the only device to measure the electricity service amount in local. This kind of attack can cause financial loss due to incorrect readings and bring dispute between the power provider and the subscriber. In this paper, we address the non-repudiation problem with respect to accountability in the neighborhood area smart grids. We propose a mutual inspection strategy which can detect problematic smart meters and prevent further financial loss. Our evaluation results show that this scheme can be effectively applied to smart grids.