Friday, May 29, 2009

GPS Evidence Q & A

Thanks to "D" for the following questions, which I will answer subject to the disclaimers on the bottom of this page, and as hypothetical situations:

Question 1:
Does the GPS receiver have to be 'sealed' or at least in official custody to prevent tampering (upload of bogus track) when used to track a suspect or gather evidence for conviction?

A: Laws vary from jurisdiction to jurisdiction, and new laws are being enacted every day. Accordingly, that would depend on both the rules of evidence in the particular jurisdiction, and on the judge the GPS track evidence was presented to for admission. If there are no statutory requirements, generally all evidence must be accounted for in a "chain of evidence." In short, this would require those who attached the GPS and collected to swear to the manner of secure clearing of the GPS unit, the manner of GPS evidence retrieval (that is, was the entire GPS recovered, or was it downloaded by phone or by close proximity secure download.) Furthermore, the officers would have to testify regarding how the GPS track sought to be entered into evidence was securely stored, then about how it was processed for display to the court or jury. I've said this before- because a GPS track is just a data file, the information it contains is only as valuable as the veracity of those swearing to it. While GPS evidence is a particular type of evidence, it is, short of a jurisdictional control, just evidence. The proffered GPS track does have to be relevant to the situation in court, and not just a "Gee, Judge, we want to wow the jury with our CSI-like abilities, even though our GPS track has nothing to do with the case we are trying. . ." Law enforcement may choose to "seal" both the GPS and any downloads of GPS to make the job of introducing the GPS track into evidence easier, but it is not required. See my blog entry on relevancy here

Of course, in Washington, Oregon, and now New York, a warrant is required to even attach the GPS to the suspect or witnesses car. I will discuss the New York case (and Wisconsin's appeal court decision that did not require a warrant for GPS tracking in a blog shortly.

Question 2:
How can a receiver be used as defense (e.g. speeding) if it wasn't taken as evidence
(I could upload more bogus track info)?

A: Again, I take this as a hypothetical. See question 1, above, that all GPS data is only as credible as the person attempting to admit it. Given that a suspect of speeding suddenly has a GPS track of himself not speeding, which he did not disclose to the officer at the scene would be highly suspect. Why did this hypothetical suspect not disclose the supposedly exonerating GPS track to the arresting (or ticketing) officer? Simple-the suspect thought it might prove he was speeding! He wanted to check it out first. If he confirms he was, then he'll likely pay the ticket.

Likely, because the suspect doesn't know how to 1) preserve the track and 2) show the track in a manner the court might find acceptable, it is unlikely a court would admit such a track after the fact. The one exception I could see-where the track is both gathered and kept by a third party, that is, a remote tracking service that has no stake in the case, no reason to lie, and a business interest in keeping accurate records. Such records would be both tamper-proof (or at least resistant) and credible. The remaining qualification-would the GPS track of a speeding suspect be relevant? See my above link on relevancy, which is highly applicable to speeding situations. In short, because GPS tracks average speeds between track log points, only an extremely "dense" track (with a lot of track points, recorded very frequently, on the order of one track point a second or every two seconds) would have the accuracy to overcome a police radar reading that, at a particular point the radar gun was pointed at the suspect, he or she was speeding.

So, hypothetically, could a suspect after the fact tamper with a track, or create a track and load it into a GPS for police consumption? I've suggested in blog posts police could "dummy-up" a track to present to a suspect. Why shouldn't a suspect do this?

Two huge reasons:
1) Police are allowed to lie, suspects are not. Police are allowed to fabricate evidence to challenge a suspect's declarations of innocence to test his story. An innocent suspect, goes the theory, will stick to his story no matter how much false evidence is before him. A guilty suspect will confess because he thinks he's been caught.

Suspects, however, are not allowed to lie to the police, or present false evidence. Its a crime in most jurisdictions, called "Obstruction of Justice" or something of the like. Uploading a "bogus" GPS track and presenting it as real or tampering with a real track is either perjury or obstruction of justice, or both. Both are very serious, not like a speeding ticket.

2) A suspect in an interrogation room won't have time or expertise to analyze police evidence put before him or her, but police will have all the time in the world to analyze GPS evidence offered by a defendant to a speeding charge. Any offered track would be, at the least, part of the police file, at most, part of the court's evidence, and would stay in the file for analysis (today, or by future, more sophisticated methods) for years.

Police Experts (and private experts) can detect "bogus" tracks, given enough time. I won't get into all the ways, but one way is the laws of physics and common sense. For instance, if a track shows someone proceeding at 60 mph but slowing so suddenly that skid marks would have to be produced to do so, (and there are no skid marks) it would be evident that a track had been tampered with. Track points are time stamped, and tiny differences make huge differences in speed. Since one track point is dependent on the previous track point position, and so on, a tampering suspect might try to show he wasn't speeding for on stretch of road, but show he was speeding two minutes earlier. This internal structure of GPS tracks helps enhance their credibility and decreases the chance tampering won't be found.

Obstruction of justice is likely a much more serious offense than speeding, and not only would a court be likely to "throw the book" at a speeder who tried to fake a GPS track on the speeding charge, he or she would also likely throw the book at the speeder for obstruction of justice.

Thanks, "D" for raising this hypothetical question.

Thursday, May 21, 2009

The Economics of GPS Evidence

Government and law enforcement budgets are being slashed. At the same time, local and government law enforcement agencies are not only expected to enforce pre-9/11 laws, they are the first line of defense against domestic and foreign terrorists. Add to this the kind of crime increases that are coupled with unemployment (property crimes, child abuse and domestic violence) and our law enforcement bodies have their hands full.

What does it take to adjudicate a crime, in terms of resources and dollars? The cost to adjudicate a criminal (or for that matter civil) case is directly proportional to the quality and credibility of the admissible evidence presented:

  1. Marginal evidence of crime probably takes the least judicial resources, because no prosecution ever takes place. However, where it is certain a crime has been committed (for instance, an unsolved murder) an uncertain case continues to take law enforcement resources, with attempts to solve the crime continuing throughout the years. Where police need to investigate if a crime was committed (for example, an unexplained disappearance with no body) law enforcement has to weigh the wisdom of investigating a possible crime with pursuing solutions to verified crimes.

  2. Evidence of either a certain crime and uncertain perpetrator, or certain perpetrator and uncertain evidence of crime take the most resources. These cases are the most likely to go to trial and most likely to involve large blocks of investigative time.

  3. With certain evidence and a certain perpetrator, the case will likely settle, although some perpetrators insist on a trial. Here, the measure of resources will be determined by how much evidence the prosecution must present to the finder of fact before satisfying the criminal burdens of proof. High quality evidence that is easy to present is the best kind of evidence.

No alleged crime investigation and prosecution stands alone-all investigations are only as good as the totality of enforcement and prosecutorial resources that can be bought to bear on a specific alleged crime in relation to all the other alleged crimes before those enforcers and prosecutors at a given time.

Evidence of crime will be judged by three audiences before a guilty verdict is rendered:

1) the suspect (Is there enough evidence, and is it believable) enough here I should take a deal and plead guilty?) 2)The officer-prosecutor (Is there sufficient credible evidence to convict beyond a reasonable doubt?) 3) The jury (Is the suspect guilty beyond a reasonable doubt?)

At one time, the eyewitness identification was the “gold standard” of high quality evidence. However, scientific testing of the general publics' observational abilities has shown eyewitness testimony is actually poor proof of criminal identification. Fingerprint evidence, still valid and high quality, is only useful where the accused is a stranger either to the environment or the particular evidence in question. DNA evidence, the new gold standard, is useful, but only under the same circumstances. DNA evidence, in addition, must go through expensive and extensive testing, often at overworked State crime labs.

How would widespread GPS evidence investigation save money, time and resources in criminal investigation and prosecution while resolving more cases and solving more crimes?

Real police work involves asking questions and interviewing people. Surveillance, however, involves waiting for hours (often with several officers) for a single event or occurrence, or high risk tailing, that is, following a suspect without the suspect detecting law enforcement presence. Both involve high numbers of officers and high hours. GPS tracking evidence, while not replacing surveillance, can focus surveillance in such a way that police can mount surveillance at known suspect destinations, and often at very specific times.

GPS evidence tracks are high quality, credible evidence, to all the audiences above.

  • GPS evidence needs very little “processing” and will be available during the investigative stage (as opposed to DNA, which may take months to process.)

  • GPS evidence is straightforward, easily displayed and explained, and extremely persuasive. While fingerprints and DNA can be explained to a jury, a jury can watch a GPS track map display from a suspect's home or last identified location right to a crime scene. A guilty suspect in an interrogation room will see this immediately, and start looking for the best plea bargain possible.

  • Indeed, some GPS evidence is available in “real time”, allowing police to either actually prevent a crime or catch a perpetrator in the criminal act, something DNA will never do.

  • GPS tracking is “cheap”-although individual GPS units might be somewhat pricey, each unit is probably less than a batch of DNA tests. GPS units are certainly cheaper than the payroll of the officers, prosecutors, court personnel and judges that less certain "marginal" evidence requires to get the same results.

  • GPS tracking evidence frees law enforcement from time consuming surveillance tasks, letting them concentrate on real police work. Remember, hours saved in one case are hours that can be devoted to other cases.

  • Finally, the quality, accuracy and persuasive force of GPS evidence resolves cases short of trial. Because it is simple and easily understood, even the most hardened criminal knows he won't have a chance with a jury when they see a track of him pulling up before the house where the rape occurred, the arson happened, or outside his ex-spouses house he was stalking. Suspects will plead guilty. Prosecutors and officers can concentrate on other crimes.

  • Previously unsolvable crimes will be solved by GPS evidence. GPS evidence is already solving crimes like remote forest fire arson, where surveillance is impossible (because it would be spotted.) Just because these cases were unsolvable doesn't mean law enforcement didn't try, using time, money & resources.

  • Given the incarceration of repeat offenders, and the possibility of detection by GPS tracking, the more GPS tracking is used, the more crime will decline. Declining enforcement and prosecutorial commitments allows more investigative scrutiny of the remaining crime, thus increasing a criminal's risk of detection, and lower crime rates. Increasing prosecutorial pressure will mean longer criminal sentences, greater enforcement pressure, and again, greater risk for the criminals-which translates to a lower crime rate.

  • Very few types of evidence can exonerate a suspect. GPS evidence can. For instance, if police have narrowed possible suspects to three people, and use GPS tracking on all three. Two have tracks that show they were no where near the crime scene; and one suspect does. No further resources need to be devoted to those exonerated suspects.

For all these efficiencies, I have to restate that GPS evidence does not solve crimes, it only narrows the relevant questions to a specific geographic area for a specific time frame, raising questions that the guilty can't answer, but the innocent can. However, because both the geographic time frame and time line are so specific, guilty suspects will know they have no chance, and plead guilty.


Legislatures must act quickly to regulate GPS tracking so that the court system will not exclude GPS evidence based on faulty- Fourth amendment analysis. Economically, its only rational to preserve this valuable investigative tool that convicts the guilty and exonerates the innocent-for pennies compared to previous investigative methods.