Wednesday, October 23, 2013

Anonymous Tips, Risks, and Type 1 Errors

by Sherry F. Colb

In my column on Verdict today, part 2 of a 2-part series of columns, I continue my analysis of the U.S. Supreme Court case of Navarette v. California.  This is a case in which the Court will decide whether anonymous tips provide a sufficient basis for stopping an allegedly reckless driver, absent corroboration of criminality.

In this post, I want to discuss Chief Justice Roberts's view of this issue and the competing risks of Type 1 and Type 2 errors.  The reason we know Chief Justice Roberts's view is that he dissented from the Court's decision four years ago to decline to grant review of a similar case, in Virginia v. Harris.  Regarding the notion of ignoring an anonymous tip about a drunk driver, the Chief Justice, joined by Justice Scalia, said the following, in his dissent from the Court's denial of certiorari:
"The conflict is clear and the stakes are high. The effect of the rule below will be to grant drunk drivers 'one free swerve' before they can legally be pulled over by police. It will be difficult for an officer to explain to the family of a motorist killed by that swerve that the police had a tip that the driver of the other car was drunk, but that they were powerless to pull him over, even for a quick check."
It is difficult not to feel the force of the Chief Justice's argument.  An anonymous tip about drunk driving gives the police the opportunity to save someone's life.   It calls the officers' attention to a potential menace on the highway, and it would understandably appear inexplicable to the family of a drunk-drivers' victim that police knew about that menace and did nothing to stop it and spare the life of a loved one.

When our existing danger-detection systems fail to identify a true danger, we call that a Type 2 error.  For example, we might have a test for breast cancer in which a doctor uses a needle to draw some cells from a breast lump and then analyzes those cells under a microscope.  Assume that the test is imperfect and that in some small proportion of cases, the cells that are drawn are normal cells, even though much of the lump is in fact malignant.  On those occasions, we would have a Type 2 error or a "miss," because our test failed to detect -- and thus failed to generate a potentially life-saving intervention in -- a cancerous process.

In such a case, Chief Justice Roberts might observe that it would be difficult for the family of the cancer patient to understand, if the patient ultimately dies of breast cancer, why doctors did not simply remove the lump.  Why look for more evidence, once doctors have found a lump in a woman's breast?  Isn't the removal of the lump substantially less harmful and destructive than a woman's death by breast cancer?

One might, of course, legitimately believe that the answer to this question is yes.  However, there is another side to the story and it is one worth examining before concluding that Type 2 errors must be avoided at all costs.

There are Type 1 errors, also known as "false hits."  Type 1 errors occur when our detection system identifies a threat when no threat in fact exists.  Take, for example, a very sensitive MRI machine, which is used to detect cancer.  It may be the case that the machine misses nothing -- that it has no Type 2 errors, in other words.  If there is any cancer, it will show up on the MRI.  On the other hand, as is often the case with systems that miss nothing, it often makes Type 1 errors (false hits), so that doctors see what may be cancer in various parts of the patient's body, but often, none of the "hits" turns out to actually be cancer.

For someone whose life is saved because a fast-growing cancer, otherwise undetectable, is found through an MRI and later removed, the worry about false hits might seem an indulgence.  That patient knows that because of the highly sensitive and reactive test he underwent, he is alive when he would otherwise be dead.

But there are likely to be other patients, perhaps many, many other patients who would feel quite differently. Those are the patients who are told that they might have breast cancer, lung cancer, or kidney cancer, for example.  Those patients are then subjected to painful biopsy procedures, each of which gives rise to a risk of infection and, in a small number of cases, a risk of death.  With enough false hits, it would plainly be inappropriate to use the MRI machine as an across-the-board diagnostic tool for cancer, despite the fact that its use might, in individual cases, save lives.  The morbidity and mortality generated by Type 1 errors can outweigh the benefits of avoiding Type 2 errors.

Could the same be said for anonymous tips?  Perhaps.  Imagine that whenever the police receive an anonymous tip indicating reckless or drunk driving, the police stop the allegedly offending vehicle, despite the absence of any corroboration (such as observed reckless driving).  Such a policy could, if there were many false anonymous tips, lead to a large number of stops of innocent drivers on the highway .

So what?,  Chief Justice Roberts might ask.  Police would pull over the driver, do a "quick check," and then allow the driver to move on, in that event.  This is not necessarily true, however.  If police believe that a driver is drunk, based on an anonymous tip, then they might ask the driver to blow into a breathalyzer.  The driver might refuse, complaining that he did not do anything wrong and does not trust breathalyzers.  What should the police do then?  If the suspect does not want to cooperate with them, they might feel compelled to arrest him.  After all, if he is in fact drunk, he could hurt someone on the highway.  An arrest, in turn, would entail additional invasions of privacy, perhaps including a strip search -- if he is brought to the general population of a jail, under Florence v. Board of Chosen Freeholders.

Traumatized by his experience, even if he is ultimately freed, this driver could develop a sense of distrust toward the police.  And with enough people experiencing this undeserved humiliation and trauma, it is easy to see how the police might become less respected, less legitimate in the eyes of the public, and thus less effective at keeping the community safe.  To the extent that police must rely on partnerships with communities to keep crime down, such a development could prove catastrophic.

Perhaps this sounds like hyperbole, and perhaps it is.  Much depends on the number of false anonymous tips (and of true anonymous tips) that police receive.  But imagine, by analogy, that patients began to distrust the medical profession, because of the many false hits that yielded painful, traumatic, and harmful investigative interventions.  This imaginary scenario is, in fact, close to reality for many patients, who have suffered the trauma of harmful, excessively invasive, and counterproductive medical interventions.  What this could mean is that patients feeling ill or experiencing disturbing symptoms might decide to avoid going to the doctor, for fear of tests, tests, and more tests that could prove more damaging than helpful.  If this happened, then the highly sensitive MRI machine and other similar tests could have the paradoxical effect of multiplying the number of Type 2 errors (misses), by driving the patient population away from doctors' offices and from the possibility of an accurate diagnosis and treatment.

With uncorroborated anonymous tips, it is very difficult to know when and how much to trust them.  Ignoring them could be extremely costly, and the costs might seem utterly unjustified and inexplicable to those who must pay those costs in the form of highway fatalities.  But we must remember, and I hope the Justices remember as well, that there are costs involved in scrupulously stopping everyone accused by an anonymous informants.  There is much room for abuse, and the consequences -- for law and order and for public safety -- could conceivably be just as disastrous as the scenario that Chief Justice Roberts envisions.  We must therefore tread carefully in this area.  The anonymous tip could prove, as promising as it might seem, to be a curse in disguise.


pvineman1 said...

In many cases an anonymous tip will contain enough detail to constitute "reasonable suspicion" justifying a brief seizure (i.e., stop) of the vehicle and its driver.

At that point, the Court should require that the seizure of the driver be as brief, and non-intrusive, as possible.

If the officer does not observe any objective signs of intoxication during his/her face-to-face encounter with the driver -- a driver who, presumably, remains seated in the driver's seat during this initial contact -- he/she may not request (or order) the driver to engage in any more intrusive conduct, such as performing field sobriety tests and/or blowing into a preliminary alcohol detector or breathalyzer.

However, if the initial, brief, door-side contact corroborates the anonymous tip (i.e., the officer observes objective indicia of intoxication or consumption of alcohol via empty liquor containers), then more intrusive procedures would be justified (such as FSTs and breath testing).

Applying this relatively simple rule would avoid many, if not all, of the potential pitfalls that are described by the writer.

David Ricardo said...

In a court decision that was released last week in North Carolina, the state Court of Appeal had to rule on whether or not evidence of DWI gathered from policing stopping a vehicle where the stop was instigated by an anonymous phone call should be excluded from the trial on DWI charges.

A cab driver made an anonymous call (the cab driver, a Mr. Hutchby was later identified by his cell phone number) to 911 and reported a car being driven in a dangerous manner, weaving and seemingly not under full control. Police later stopped the car and after interviewing and questioning the driver charged him with DWI. The driver later pleaded guilty subject to an appeal that the evidence gathered from the stop should be excluded because the police did not have reasonable cause to stop him.

The North Carolina appeals court ruled in favor of the driver.

“In the instant case, Officers Jones and Kanupp did not personally observe any unlawful behavior by defendant or have the opportunity to meet Hutchby prior to the stop. Since the 911 operator was able to establish Hutchby's identity by tracking the personal cell phone he used to make the call, the officers later discovered Hutchby's identity. The officers were also unable to judge Hutchby's credibility and to confirm firsthand that the tip possessed sufficient indicia of reliability. Since Hutchby's anonymous tip did not possess sufficient indicia of reliability, Officers Jones and Kanupp did not possess reasonable, articulable suspicion to stop defendant's car”

This is the exact situation Ms. Colb has described in her post, and despite Ms. Colb’s arguments in her post, this is very disturbing. An impaired driver is highly dangerous, akin to an individual armed and running around shooting randomly. Suppose police receive an anonymous call that describes an individual who is running around and firing a gun. Are the police to be prohibited from accosting and questioning a person that fits the description even though no gun is evident when they find that person? In either situation damage to innocent people will not necessarily occur, but it might. Society has a right to be protected against random shooters and to be protected against drivers who are impaired.

There is a balance that must be struck here between the rights of society to prevent harm and the rights of an individual, but given the horrendous damage that can be done by a drunk driver and the relatively light intrusion on the right to be free from unreasonable search, it would seem that the rule of law comes down rather clearly on the side of society. Driving is a privilege, not a right. Police acting on an anonymous tip about erratic and possibly dangerous driving should have the right to stop and investigate. The cost to society of allowing drunk driving is just too great.

pvineman1 said...

When a witness calls 911 to report a DWI suspect or a reckless driver, his/her call is really not "anonymous." The government can easily ascertain the identity of the caller, whether or not the call was placed from a cell phone or a traditional telephone.

It is also reasonable to assume that everyone knows that when they call 911 to report a crime that the police will be able to determine their identity, regardless of whether or not they provide their true name. Also, every state makes it a crime to provide false information to law enforcement.

When one considers that the 911 caller's identity is readily ascertainable and that falsely reporting suspected criminal activity to the police constitutes a crime, the information provided by the so-called "anonymous" caller is presumptively reliable, such that it provides "reasonable suspicion" justifying a brief, Terry-like, seizure/stop of the suspect vehicle and face-to-face contact with the driver.

Respectfully, to the extent Prof. Colb is suggesting otherwise she is wrong.

Matt_Estrin said...

How does Illinois v Gates not answer the question for the defendant? Even in giving an easier test for probable cause (totality of the circumstances) the Court said the anonymous letter alone wouldn't be enough because there was nothing to establish that the person was honest and reliable. Only corroborating evidence added to it was enough to establish ToC.

That seems no different here. The tip itself is not enough. The police need to verify it by noting some semblance of dangerous driving for themselves.

Roberts claim seems particularly irrelevant. Sure it might be good policy wise, but the 4th A. requires probable cause. There is no balancing test of the cost and benefits of a rule. Either it establishes probable cause or it doesn't.

David Ricardo said...

Obviously the 4th Amendment was not written in a time that involved the technology that we have today, there were no drunk drivers in the 18th century. And the 4th Amendment was written at a time when government officials were a threat to just randomly accost citizens for no apparent reason other than the fact that they had the power to do so.

The great genius of the Constitution is that it is a document of principles, not procedures and those principles must be applied to an evolving culture. (sorry Mr. Scalia, you are just plain wrong.) Furthermore those principles must adjust to reality, as they do. For example, the threat of imminent harm or destruction of evidence in some situations is enough to allow exceptions to basic rights. Police may enter premises and conduct searches under certain circumstances without a warrant.

In the case of a traceable telephone call warning of erratic driving it would seem that this is sufficient cause for the police to stop and investigate that driver. Requiring officers to obtain further information on the caller increases the risk that the drivers will do damage to others and themselves. And since the concept of erratic driving is in the mind of the observer, simply requiring officers to follow and observe before stopping adds nothing to the process, the officers can always say they thought the driving was erratic.

It would be nice if the Constitution were simply a recipe for behavior. It is not.

Unknown said...

When one considers that the 911 caller's identity is readily ascertainable and that falsely reporting suspected criminal activity to the police constitutes a crime, the information provided by the so-called "anonymous" caller is presumptively reliable, such that it provides "reasonable suspicion" justifying a brief, Terry-like, seizure/stop of the suspect vehicle and face-to-face contact with the driver. Buy Fifa 14 Coins
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Anonymous said...

That seems no different here. The tip itself is not enough. The police need to verify it by noting some semblance of dangerous driving for themselves.
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