Gina McCarthy testifies on Thursday. (Joshua Roberts/Reuters)

Appointees, here’s a good defense against potential accusations of technological malfeasance: being too dang old to understand how the gizmos work. That is, you can’t misuse technology if you don’t know how to use it at all.

That was the stance of deputy Environmental Protection Agency administrator Gina McCarthy, who testified Thursday before a Senate committee on her nomination to helm the EPA. There, she was grilled about the use of personal e-mail accounts to do public business — something Republicans have hammered other EPA officials about.

After McCarthy assured the panel that she never used her private account improperly to do government business (which, critics fear, might shield said dealings from scrutiny), Sen. David Vitter of Louisiana, the top Republican on the Environment and Public Works Committee, asked her whether the same held true for instant messages.

And that’s when she invoked the geezer defense.

“One good thing about being 58 is that I don’t even know how to use them,” she admitted, to laughs from the audience. “I don’t know how. Sorry. You’ve got to admit it.”