I've seen quite some low market cap stocks that closed on day high almost every day because of a single buy order just before the closing bell. Sure this is reflected in the charts, but you should look at volumes as well. If such situations happen on a daily basis on low volumes, then I don't consider it a sustainable uptrend.

There really is no law that always applies in technical analysis, but there are some theories that can increase your chances of success. I enjoyed reading Technical Analysis for the Trading Professional by Constance Brown, can recommend to anyone.