Since the release of the Nunes Memo on Friday, people on both sides of the political divide have been laboring to persuade the public that the facts alleged therein are, or are not, proof of sinister (or at least questionable) motives on the part of some in the FBI and the Justice Department. Like much else in life, one’s interpretation of the Nunes Memo may depend on which side of that divide one places himself.

So, with the acknowledgement that I am a conservative and susceptible to bias toward the corresponding interpretation, let me explain why I find the Nunes Memo troubling.

First, a note about my own experience. I spent more than 30 years with the Los Angeles Police Department, a significant portion of which was spent in specialized detective assignments in which I wrote hundreds of search warrants. I also participated in investigations pursuant to FISA warrants, though in none of these was I an affiant or source of information. Now having retired from the LAPD, I am working full time with a law enforcement agency in a neighboring jurisdiction, and I still investigate crimes and write search warrants.

That said, the principles governing FISA warrants are, at bottom, no different from those that apply to warrants in more mundane criminal cases. For a warrant to be granted, an affiant must present to an impartial magistrate sufficient proof that a person is involved in criminal activity, and that an intrusion on the target’s constitutional rights, whether through a search or surveillance, is called for.

It has long been my practice to use informants sparingly. As many police officers have learned too late, if you use an informant long enough, it’s only a matter of time until he embarrasses you. An overly credulous police officer can place too much trust in an informant and be led astray, especially if the informant produces good results in the early going.

Still, the use of informants is sometimes inescapable, and when an informant does provide information to be used in a warrant, a police officer must demonstrate to a judge’s satisfaction that the information is reliable. This can either be done by showing the informant has a record of giving information that has proven true, or by independently corroborating the information.

In a typical scenario, an informant tells a police officer that a specific person is selling drugs or that drugs are being sold at a specific location. If the informant is “reliable,” i.e., has established a record of being truthful and accurate, no corroboration is necessary to obtain a warrant (though it is wise to seek corroboration anyway).

If the informant has no track record, the information he provides must be corroborated, most commonly through surveillance. For example, if an untested informant alleges drug sales at a certain house, a police officer might watch the house for a period of time and observe activity consistent with drug sales, such as people arriving and leaving after only a short visit. Some of these people might be stopped in the hope of recovering the drugs they have bought, and with the possibility of turning them into informants themselves.

But a police officer must be wary of being “played” by an informant, whose true motives may be unknown to the officer. An informant might be involved in the drug trade himself and provide the police with information on rivals in the hope of eliminating the competition. Or he may hope to divert police attention from his own criminal enterprises. I’ve known colleagues whose informants provided information resulting in the seizure of a few pounds of drugs, only to have the informants themselves arrested in another jurisdiction with hundreds of pounds.

The rule to observe is simple: Never trust an informant completely, no matter how reliable he may have been in the past or how juicy his current tip may be.

We may never know the extent to which this is true, but my suspicion is that Christopher Steele played the FBI, some members of which were insufficiently skeptical about his information.

It was Steele, the former MI6 agent who, according to the Nunes Memo, provided the basis for the FISA warrant targeting Carter Page. As a former intelligence officer, Steele would be familiar with the language needed to arouse interest in the FBI, and his credentials may have lent him more credibility than his information should have been accorded. Indeed, as Andrew McCarthy points out at National Review Online, Steele was not the actual informant for the FISA warrant. Rather, he was the purveyor of hearsay information supplied to him by other unknown and untested informants.

Such information is insufficient for a finding of probable cause absent corroboration. The Nunes Memo makes the claim (challenged in the Washington Post here) that the FBI’s corroboration came in the form of a Yahoo News article — the source for which was Steele himself.

A final point: As I said, the use of informants is sometimes unavoidable, and in criminal cases precautions must be made to protect an informant’s identity, both to ensure against retaliation and to maintain his access to valuable information. When writing an affidavit for a warrant, the affiant must take care to provide enough detail to persuade a magistrate that the information provided is accurate, but not enough to allow the target to deduce the informant’s identity. A certain amount of obfuscating language is called for and expected, for the affiant knows the warrant will be discovered and challenged in court if it results in charges being filed.

But in the case of a FISA warrant, there is no expectation of a court challenge.

Indeed, there is no expectation that the warrant’s very existence will be known to anyone outside a small circle in the FBI and the Justice Department. There was thus no need to use obfuscating terms like “political entity” in describing the origins of the Steele dossier, unless people in the FBI and the Justice Department were concerned that the warrant would not be granted if the full truth about its underlying information were known to the judge.

Perhaps the full warrant application will be made public one day, in which case there may still be conflicting opinions on whether the government’s burden to show probable cause was met. But what is already known about the case — when added to the Bill Clinton-Loretta Lynch meeting on the tarmac on Phoenix, James Comey’s sophomoric tweets, and the FBI’s and DOJ’s intellectual and legal contortions in declining to prosecute Hillary Clinton for the reckless handling of her email — suggest an FBI and Justice Department with their thumbs on the scale of justice.

You don’t have to wear a MAGA hat to find all of this troubling.