Research into ancient mitochondrial DNA is plagued by contamination, post mortem damage, and other artefacts. The stringent set of controls suggested by Cooper and Poinar a few years ago are, however, rarely followed in practice, and even when applied carefully, these criteria need not be sufficient to guarantee authenticity. The fairly relaxed prerequisites now common for ancient population studies have opened the door for all kinds of contamination and sequencing errors to enter ancient mtDNA data. To reject or question authenticity of particular sequencing results a posteriori, one can follow similar strategies of focused database comparisons that have proven to be effective and successful in the case of flawed modern mtDNA data.