I believe your conclusion is in error. [=incorrect, mistaken]我认为你的结论是错误的。

The judge was in error when she allowed the evidence to be admitted.女法官判断失误，允许了那项证据被采纳。

My earlier statement was made in error. [=my earlier statement was incorrect]我先前的陈述有误。

The evidence was admitted in error. [=incorrectly, mistakenly]那项证据被错误地采纳了。