EvidenceProf Blog

Editor: Colin Miller
Univ. of South Carolina School of Law

Friday, June 30, 2017

Maryland Court Finds Evidence & Testimony Related to Cell Tower Drive Test Unreliable and Inadmissible

Two days ago, the Court of Special Appeals of Maryland issued an interesting opinion in Phillips v. State. In Phillips, Bashunn Phillips was charged with the first-degree murder of Shar-Ron Mason and related crimes. 

The State notified Phillips that it intended to offer at trial a radio frequency (“RF”) signal propagation map purporting to establish the approximate location of Phillips’s phone on the morning of December 10, 2013 [the day of the murder]. The propagation map represented data obtained through a drive test conducted by Special Agent Richard Fennern, a member of the Federal Bureau of Investigation’s Cellular Analysis and Survey Team, on October 23, 2014.

In response, Phillips filed a motion in limine, "seeking to exclude the RF signal propagation map and related testimony."

In support of this argument,

William Folson testified for the defense that the State's use of the drive test was not generally accepted in the forensic science community....At the time of his testimony, Mr. Folson was a professor of digital forensics and a doctoral student in information assurance, with a focus in digital forensics....He was also board certified in digital forensics, certified in cyber forensics, and certified in cellular technology and mobile evidence....Mr. Folson testified that drive tests were "a waste of time" for forensic purposes, because radio frequency signals constantly change due to such variables as weather, topography, the amount of cell phone calls being made in a particular area, the power output of a cell phone tower, the type of antenna used on a tower, foliage, and surrounding buildings....Moreover, coverage areas of different cell phone towers may overlap....[According to Folson:]

[R]adio frequency signals…fluctuate. They get stronger, they get weaker in real time. So, there is no way to calculate what the signal strength was ten months prior doing a drive test....So, that drive test is a snap shot of the [radio frequency] footprint for that tower at the time the test is done. It has nothing to do with what the [radio frequency] signal footprint was ten months prior to that test being performed.

Mr. Folson further testified that he was unaware of any peer-reviewed scientific articles or reported Maryland appellate case supporting the use of drive tests for determining the radio frequency of a cell phone tower on a certain date in the past....[According to Folson:]

We know that the cell phone companies use drive testing, and I would absolutely agree that a drive test has value to a cell phone company. However, you're taking a drive test and you're repurposing this diagnostic tool for a forensic methodology that has never been suggested to peer review and has never been accepted by the scientific community. That's the issue.

Based upon this testimony, the trial judge "concluded that the State did not establish that drive tests as used by the FBI are generally accepted in the digital forensic science community"*and therefore deemed the propagation map and related testimony inadmissible.

The State responded by seeking "in banc review of the order granting Phillips’s motion in the circuit court." The State was actually granted such review, on that review led to the trial judge's conclusions being reversed. In turn, Phillips appealed to the Court of Special Appeals of Maryland, which issued its opinion two days ago. According to the three judge panel (including Judge Graeff, one of the judges handling the appeal in the Adnan Syed case), "the State had no right to appeal from the trial court order granting Phillips’s motion in limine," so the in banc panel was without jurisdiction."

As a result, the court reinstated the trial judge's order deeming the evidence related to the drive test inadmissible and remanded the case back down to the trial court so that FolsonPhillips's trial can be held...without the drive test evidence.

Of course, anyone following the Adnan Syed case knows that a drive test was part of the State's case against Adnan; indeed, it was part of "the crux" of the State's case according to Judge Welch. Because the Court of Special Appeals didn't reach the merits of the drive test claim in Phillips, it didn't create a new precedent that could be cited by the defense at a new trial or on appeal. But the Phillips case certainly provides a good indication that anything connected to the drive test by the State's cell tower expert in Adnan's case could be deemed inadmissible if a new trial is held.


*The judge also "mused that, even if the drive test were considered generally accepted and reliable, the State’s experts were not qualified to testify because they were not members of the digital forensic science community and failed to satisfy the requirement of Maryland Rule 5-702."



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It seems to me that this belief that cell phone RF topography can be used as a physical location indicator from the past is at least in part due to the way cell phones are presented in marketing and therefore perceived by the general public. Cell phone services are sold based on the reliability and range of their coverage, so the entire system is engineered to provide the end-user with a consistently reliable source of signal that seems to them to be completely static. But it isn't a static system, it is just designed to appear that way because cell phone users want their phones to just work no matter where or when they are. But in point of fact, there are many variables at play in the system that affect the range and reach of the signals, as mentioned above: weather, foliage, system load, terrain, physical structures, line of sight, etc. It's just that the system is designed to take all of those things into account and adapt to the current conditions, so it APPEARS to be a constant, static signal source from the point of view of the end-user.

But like Mr. Folson said: as a diagnostic tool, the RF topography map is a very useful tool to help the engineers design and improve the system so that it can provide and maintain consistent and reliable coverage in any possible conditions, but to use this tool to somehow see into the past is a ridiculous notion at best. It just doesn't work that way. It is basically akin to looking at today's weather and concluding that ten years ago on this date it must have been raining because it is raining today.

In any case, I agree that this looks like an indicator that things are moving in the right direction for Adnan. I think that you and the others have done your best to fight for what is right, and I have to believe that commitment will pay off; otherwise, what is the point of the system if it doesn't acknowledge the truth eventually, even if it is far past due?

Posted by: Kevin | Jun 30, 2017 1:09:51 PM

Read the last full sentence on page three of the opinion as well as footnote 5. You must have known this is a different kind of test than what was in Adnan's case. Why didn't you mention that?

"Phillips acknowledged that cell phone tower “ping” evidence is admissible, but drew a distinction between the method used to create the RF signal propagation map and the collection of historical cell phone “ping” evidence.5"

"5 Cellular tower “ping” evidence is deemed reliable and is admissible without a Frye-Reed hearing. See Stevenson v. State, 222 Md. App. 118, 133 (2015)."

Posted by: Steve | Jul 1, 2017 4:58:32 AM

That is great news

Posted by: Linnette garber | Jul 1, 2017 6:15:29 AM

At argument, both the three-judge in banc panel and the three CSA judges agreed the trial court's decision was absurd and indefensible on the merits. Your desire to see Adnan get away with murder has caused you to grossly distort this decision.

Posted by: Lex Apostata | Jul 1, 2017 6:37:35 AM

Kevin: Thanks.

Steve: I’m not sure what you mean. I think we both agree that properly qualified experts can give testimony about what cell tower was pinged by a certain call (e.g., the 2:36 P.M. call on Adnan’s call log). The argument by the expert that was accepted by the trial judge in Phillips was that testimony regarding road testing conducted months after that call is not reliable/admissible "because radio frequency signals constantly change due to such variables as weather, topography, the amount of cell phone calls being made in a particular area, the power output of a cell phone tower, the type of antenna used on a tower, foliage, and surrounding buildings.” In both the Phillips case and Adnan’s case, there was road testing done after the call(s) in question.

Linette: We’ll see where the Phillips case goes from here.

Lex Apostata: I noted in my post that (1) the in banc panel disagreed with the trial judge on the issue; and (2) the three judge COSA panel did not address the merits of the issue because it found that there wasn’t jurisdiction for the State’s appeal. Legally speaking, this means that there’s no ruling on the merits other than the trial judge’s ruling. Factually speaking, of course, you’re free to disagree with the defense expert and the trial judge.

Posted by: Colin Miller | Jul 1, 2017 10:03:59 AM

@steve if I remember correctly, the state had large blown up maps of cell coverage areas for all the relevant towers. If these maps weren't created through drive testing, then how pray tell were they created?

@lex apostates: if you bothered to read the article, rather than furiously diving down to the comment section to mash out a butthurt reply, you'd have noticed that exactly what you said was, in fact, fully explained in the article. Good job!

And additionally, I must point out again the reliance of guilters' arguments on everyone they disagree with "wanting to help a murderer get free". I mean if you listen to them, a majority of people who know about the case, judges included, all want so badly to get a murderer out of prison.

Note that they aren't just honestly mistaken, no no no! In order for their belief set to actually work it requires that Susan, Colin, Rabia, Asia, Judge Welch, you name it, pretty much everyone who isn't a subreddit devotee, to on a regular repeating basis knowingly lie about everything under the sun, all in the 100% conscious goal of setting a murderer free. Yaknow, cuz that makes so much sense.

[Heres a free hint: If you must believe something so patently absurd about many different rational humans' motives, all in order to continue forcing the awkward square peg of your own preferred conclusion into the unforgiving round hole of logic+reality.... well, that potentially might be seen as a red flag by some.... Just a thought.]

Posted by: Paul | Jul 1, 2017 8:09:54 PM

I mean, just because I know Don's Flickr account has a diagram of the trunk area of late 90s sentra, clearly indicating he is participating in the online discussion, I certainly don't believe the other guilters are trying to help a murderer continue to evade justice. They probably don't even know which one he is amongst them.

Posted by: Paul | Jul 1, 2017 8:22:10 PM

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