This is, in effect a defense of mistaken identity, and an assertion that the person on trial is not in fact the person who committed the crime.
It is not legally significantly different from a case where the defendant claims that a witness has identified the wrong person.
Exactly how the defense would be conducted would depend on what evidence establishes ...
For the 12-Month Period Ending September 30, 2019 there were 16 trials for homicide in US District Courts.
I found the data in Table D-4. U.S. District Courts—Criminal Defendants Disposed of, by Type of Disposition and Offense
This page has a list of past publications. This is the most recent data from the 12-Month Period Ending September 30, 2019.
There are not comprehensive statistics that are maintained on this at either the federal level, or in any U.S. state.
It would not be possible to determine this from PACER records in federal court, or from state court online filing system records in many state courts, because both of those systems are geared towards tracking document filings in the court ...
It is not permissible to lie in court in England and Wales. See rule 1.4 of the SRA's Code of Conduct:
You do not mislead or attempt to mislead your clients, the court or
others, either by your own acts or omissions or allowing or being
complicit in the acts or omissions of others (including your client).
A lawyer is obligated to accurately state the law as stated in the jury instructions in closing argument (and also not to make a clear and deliberate misstatement of the facts presented at trials, and also not to express personal knowledge of the facts based upon anything other than what the jury has seen).
But a certain amount of poetic license is allowed ...