Today the Home Secretary got her facts wrong about a cat.
Speaking to the Conservative Party conference, Theresa May said :
We all know the stories about the Human Rights Act. The violent drug dealer who cannot be sent home because his daughter - for whom he pays no maintenance - lives here. The robber who cannot be removed because he has a girlfriend. The illegal immigrant who cannot be deported because - and I am not making this up - he had a pet cat.
This story - one of a number of myths which those hostile to human rights law invoke without ever bothering to actually check - has been published before in newspapers, and it has already been dealt with by respected critical sites such as Full Fact  and Tabloid Watch . All this was available to her speechwriters.
But what makes it worse is what was also known to her very own department.
The full determination of the Asylum and Immigration Tribunal is here [PDF ]. As Barry O'Leary, Partner at Wesley Gryk Solicitors, who acted for the foreign national, explains:
This case was not decided on the basis of a cat. It was decided on the basis of a Home Office policy which the Home Office themselves had failed to apply. This was accepted by the Home Office before the Immigration Judge and the Home Office agreed the appeal should be allowed. The ownership of a cat was immaterial. Any press reports to the contrary are, unfortunately, not based on fact.
The case involved a foreign national in a long term committed relationship with a British Citizen (they had been living together for four years at the time of the appeal.) He was not a foreign national prisoner.
I had made an application on the foreign national's behalf for the right to remain in the United Kingdom on the basis of a Home Office policy known as DP3/96.
The application was refused [by the Home Secretary] and my client appealed against that decision.
As part of the application and as part of the appeal, the couple gave detailed statements of the life they had built together in the United Kingdom to show the genuine nature and duration of their relationship. One detail provided, amongst many, was that they had owned a cat together for some time.
The appeal was successful and when giving the reasons for the success the judge did comment on the couple's cat. It was taken into account as part of the couple's life together.
The [Home Secretary] asked for the decision to be reconsidered. They argued it should be reconsidered because the decision was wrong in law, and one error they cited was that too much consideration was given to the couple's cat.
The [Home Secretary] was given permission to put the arguments to the tribunal and the decision of the tribunal is that of [Senior Immigration Judge] Gleeson.
It was decided by [Senior Immigration Judge] Gleeson that the first judge's decision was correct. As is clear from the determination, she came to this decision because the [Home Secretary] in refusing the application had not applied their own policy DP3/96 (which had been withdrawn but the transitional provisions should have been applied to my client).
It was made clear by the initial judge and then by [Senior Immigration Judge] Gleeson that the Appellant should benefit from that policy and be granted the right to remain.
Furthermore, it was accepted by the Home Office representative at the hearing before [Senior Immigration Judge] Gleeson that the policy should apply and any other errors in the initial decision by the judge (including too much detail on the cat) were immaterial.
See paragraph 6 of the determination. It makes clear that it is the former policy DP3/96 which is the basis on which the appeal was won.
[Senior Immigration Judge] Gleeson does go on to make a joke about the cat, clearly because she recognized that the discussion of the cat was irrelevant to the serious issue of applying Home Office policies correctly.
This case was won because the Home Office had a policy which they did not initially apply but later, through their representative, they accepted should have been applied.
What this means is that not only was the cat immaterial to the tribunal decision for the foreign citizen to remain, but that the Home Secretary's own representative fully accepted that the cat was immaterial to the decision.
So the Home Secretary in making her speech today not only got the facts of the case wrong, she also said something known by her own department to be untrue.
And I am not making this up.
David Allen Green is legal correspondent of the New Statesman