Please link to one&#x2F;some of the papers you are referring to. From what I have seen, they always detect edits in the controls or fail to report enough information to say either way, eg:<p>&quot;Although rare (∼1–2%), edits were detected with Cas9-only control treatment, including at the predicted CXCR4 cut site, potentially indicating trace amounts of experimental contamination of the Cas9 RNPs.&quot;
<a href="http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;33&#x2F;10437.full" rel="nofollow">http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;33&#x2F;10437.full</a><p>Note the curiously missing rows in dataset S1.