A certificate of analysis, like any other certificate, is as valuable as the issuer and the trust you place in the issuer. A COA from a company that you do not have a relationship with and which does not have a track record of ethical behavior is unreliable. In the absence of trust you can rely on raw analytical data and for that reason we generally try to provide this raw data or use well known contract labs for our third party analysis.
In the absence of trust and data you should not trust a certificate of analysis. A reputable company or lab should be able to provide raw analytical data. This comes up frequently in wholesale trade where a middle-man trading company provides a COA they made themselves in a PDF editor. Since the certificate is counterfeit they cannot provide raw data. They cannot tie it to a reputable third party lab. They cannot answer technical questions. If pressed they may deepen the lie and steal a spectra or chromatogram from the internet and present it as their own. How do you know the spectra or chromatogram is not real? It is usually obvious, look at the dates, the file names involved, the sample name, run a google image search, or ask someone with the expertise to read analytical data.
Keywords: Why are Chinese COAs useless?