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personpersonJohn SawickiJohn SawickiDigital-forensics and cell-tower expert who testified for Sigfredo Garcia in the Garcia/Magbanua 2019 trial and was listed but never called by the defense in the 2022 Magbanua retrial.← All People
Expert witness

John Sawicki

Courtroom still of John Sawicki.

Digital-forensics and cell-tower expert who testified for Sigfredo Garcia in the Garcia/Magbanua 2019 trial and was listed but never called by the defense in the 2022 Magbanua retrial.

AppearedGarcia–Magbanua
MentionedMagbanua Retrial
154 lines·8 proceedings·4 mentions·2 trials

About

Sawicki's testimony provides a sustained explanation of the limits of the phone evidence — what a gap between carrier records and an iCloud extraction does and does not prove, and how far cell-tower activity can narrow a phone's location. Because he stated those limits under both direct and cross-examination, his testimony is a useful reference point for anyone tracing how the digital and cell-site evidence was contested.

John Sawicki is a defense-retained expert in digital forensics and cell-site analysis whose background spans law enforcement, legal and academic work, training, and prior courtroom testimony. In the Garcia/Magbanua 2019 trial he was called by Saam Zangeneh as the second defense witness on Day 8, after the State rested and the court denied both defendants' motions for judgment of acquittal, and the court recognized him as an expert without voir dire from the prosecution. His direct testimony covered two subjects: a comparison of AT&T call-detail records against Charlie Adelson's iCloud data — 3,084 carrier-listed SMS/MMS events against 1,241 in the iCloud comparison for May 1 through June 20, 2014, and 1,587 against 789 for June 18 through July 18 — and Katherine Magbanua's July 19 phone activity on a Biscayne Boulevard tower roughly two-thirds of a mile from Jessica Rodriguez's home, a tower her phone used about 1,100 times between May 2014 and September 2015. He identified WhatsApp, Threema, and FaceTime in the iCloud data and said he could not rule out direct communication between Adelson and Luis Rivera through those channels. Christopher DeCoste examined him briefly for Magbanua on general network principles — that a phone selects the strongest, cleanest signal rather than the nearest tower, and that coverage can extend ten miles or more depending on geography and load. Under cross-examination by Anna Norris he clarified that the iCloud gap showed events were not present rather than proving deletion, that the aggregate carrier count had not excluded voicemail notifications and involved no content-level verification, and that the July 19 activity and historical tower counts could be consistent with visits to Jessica Rodriguez's home. Judge Hankinson noted on the record that the 11.5 percent figure counted instances, not usage time. His qualified phrasing — "could be," "consistent with" — ran through every phase of his testimony, offered to narrow the inferences available from the State's phone evidence rather than to advance an affirmative alternative account. In the 2022 Magbanua retrial he never reached the stand: defense co-counsel Christopher DeCoste first raised his availability as uncertain during a scheduling discussion and retracted the concern after receiving a clarifying email, then later announced with the jury out that the defense would not be calling him, giving no explanation specific to him.

Trial Record (8)

GMGarcia–MagbanuaSep 26, 2019 – Oct 11, 2019Called by defense

Testified on Day 8 as Sigfredo Garcia's retained digital-forensics and cell-tower expert, comparing AT&T call-detail records against Charlie Adelson's iCloud data and addressing what cell-tower activity can and cannot establish about a phone's location.

Day 8

ProceduralState Rests and Judgments of AcquittalMentioned

Summary

The prosecution formally rested its case-in-chief; both Garcia and Magbanua moved for judgment of acquittal on all counts; the court denied both motions; and the jury was informed the defense case would begin.

Mentioned in this proceeding.

DirectJohn SawickiSaam Zangeneh9highlights110lines spoken

Summary

Garcia's expert found large CDR/iCloud count gaps for Adelson, identified off-carrier apps, and described Magbanua's frequent historical use of the Biscayne tower; he did not establish why events were absent, any direct Adelson-Rivera contact, or Magbanua's exact July 19 location.

Highlights (9)

procedural actionZangeneh tendered Sawicki as an expert in digital forensics and cell tower analysis; the prosecution waived voir dire and the court accepted him without challenge.Open in transcript →Watch this moment ▶
testimony highlightSawicki revealed that between May 1 and June 20, 2014, Charlie Adelson's AT&T CDR showed 3,084 SMS and MMS messages while his iCloud contained only 1,241 — leaving more than 1,800 messages unaccounted for.Open in transcript →Watch this moment ▶
Quote“Let me — for the call detail report from May 1st to June 20th, there were 3,084 SMS and MMS messages. Within the iCloud, there were 1,241.”— John SawickiThis quantified the first CDR/iCloud comparison: 3,084 carrier-listed SMS/MMS events versus 1,241 in the iCloud data for the stated date range. It did not determine why the gap existed.Open in transcript →Watch this moment ▶
testimony highlightFor June 18 through July 18, 2014, Sawicki compared 1,587 CDR-listed SMS/MMS events with 789 in the extraction, a gap of 798. He said the events might have been deleted or might not have backed up for another reason.Open in transcript →Watch this moment ▶
Show all 9 highlights
Quote“There's not.”— John SawickiSawicki could not account from his comparison for what the absent events said or who they involved. He later clarified that deletion was only one possible reason they were not captured.Open in transcript →Watch this moment ▶
testimony highlightSawicki found evidence of WhatsApp, Threema, and FaceTime in Adelson's iCloud. Those apps would not appear as calls or texts in carrier detail records, and he could not exclude the possibility of direct Adelson-Rivera communication through them.Open in transcript →Watch this moment ▶
Quote“I can't exclude that possibility.”— John SawickiSawicki could not exclude direct contact through the identified apps. The answer established a possibility, not that such contact occurred.Open in transcript →Watch this moment ▶
testimony highlightSawicki testified that Magbanua's phone used the Biscayne Boulevard tower approximately 1,100 times between May 2014 and September 2015 — about 11.5% of tracked antenna activity, her third most used tower — contextualizing the prosecution's July 19 location theory.Open in transcript →Watch this moment ▶
Quote“Yeah, it's about 11.5% of the overall antenna usage that they were able to track. And what I mean by that is there's a number of calls for which Sprint hasn't recorded the antenna that's actually being used. So for those that they're actually able to establish a tower, about 11.5% — it was actually the third most used tower.”— John SawickiThe historical count contextualized the July 19 tower activity. The defense used it to challenge a location-specific inference, but frequency alone did not establish that the July 19 use was routine travel.Open in transcript →Watch this moment ▶
CrossJohn SawickiChristopher DeCoste4highlights12lines spoken

Summary

DeCoste cross-examined Garcia's digital forensics expert Sawicki on behalf of Magbanua, extracting testimony that phones connect to the strongest signal rather than the nearest tower, that network congestion can redirect connections to a different tower entirely, and that a single tower's coverage can extend ten or more miles — all aimed at undermining the prosecution's use of Magbanua's July 19 Biscayne Boulevard tower hit as location evidence.

Highlights (4)

testimony highlightSawicki explains that phones connect to the tower with the strongest, cleanest signal — not necessarily the closest one — and that any location can be served by multiple towers depending on network conditions at that moment.Open in transcript →Watch this moment ▶
Quote“Your question kind of anticipates that you would only connect to one tower from a particular location. It's certainly not the case. You could connect to a number of towers from any particular location, depending on where you happen to be in the circumstances at a particular time.”— John SawickiSawicki rejected the assumption that one location can connect only to one tower. His answer limits precision but does not mean a tower event corresponds to no geographic range.Open in transcript →Watch this moment ▶
testimony highlightSawicki agreed that, depending on the tower and location, coverage can extend ten or more miles. DeCoste used the answer to challenge precision, not to establish that the July 19 activity carried no location information.Open in transcript →Watch this moment ▶
Quote“Depending on where you're at, absolutely. Absolutely.”— John SawickiSawicki agreed that some towers can reach ten or more miles depending on conditions. The answer did not specify the range of the Biscayne tower for this event.Open in transcript →Watch this moment ▶
CrossJohn SawickiAnna Norris5highlights22lines spoken

Summary

Norris qualified the CDR/iCloud count and obtained Sawicki's agreement that Magbanua's July 19 tower activity could be consistent with Rodriguez's home; the testimony did not place her there.

Highlights (5)

Quote“Consistent with not being there.”— John SawickiSawicki qualifies his own deleted-message testimony on cross, specifying the iCloud gap is consistent with messages 'not being there' rather than affirmatively proving deletion — a precision the prosecution used to soften the finding.Open in transcript →Watch this moment ▶
testimony highlightNorris established that Sawicki's 3,084-event CDR count was an aggregate total and did not exclude occasional voicemail notifications appearing as text events, limiting the precision of the CDR/iCloud gap.Open in transcript →Watch this moment ▶
admissionSawicki agreed that his review found no evidence of Charlie Adelson-Luis Rivera communication. The answer described the reviewed record and did not prove that no contact occurred through any channel.Open in transcript →Watch this moment ▶
admissionSawicki agreed that the July 19 tower activity could be consistent with Rodriguez's home and that the historical antenna count could be consistent with Magbanua visiting there. He did not say either fact established her presence.Open in transcript →Watch this moment ▶
Show all 5 highlights
Quote“There's certainly activity during that time period that could be, yes.”— John SawickiSawicki agreed only that the activity could be consistent with Rodriguez's home. The answer supported a possible location but did not place Magbanua there.Open in transcript →Watch this moment ▶
RedirectJohn SawickiSaam Zangeneh5highlights10lines spoken

Summary

Zangeneh established that Sawicki had reviewed none of Rivera's phones and lacked all associated numbers, then elicited general possibilities involving deleted FaceTime records and disposable phones; no Adelson-Rivera contact was established.

Highlights (5)

testimony highlightSawicki had analyzed none of Rivera's phones and did not have all numbers associated with Rivera. That limited the scope of his no-evidence answer but did not establish that contact occurred.Open in transcript →Watch this moment ▶
Quote“None.”— John SawickiSawicki had analyzed none of Rivera's phones, which limited the scope of his review. The answer did not show that the records he did review excluded Rivera entirely or that contact occurred.Open in transcript →Watch this moment ▶
testimony highlightSawicki agreed that a FaceTime record could potentially be absent from iCloud if deleted immediately. No particular FaceTime call or deletion was identified.Open in transcript →Watch this moment ▶
Quote“Correct.”— John SawickiSawicki confirmed a general possibility that an immediately deleted FaceTime record might not remain in iCloud. He did not identify an Adelson-Rivera call or intentional deletion.Open in transcript →Watch this moment ▶
Show all 5 highlights
rulingNorris objected to Zangeneh's question about disposable phone use by criminal actors on lack-of-foundation and speculation grounds; the court overruled, allowing Sawicki to confirm that drug dealers and gang members routinely use disposable phones.Open in transcript →Watch this moment ▶

Day 9

ProceduralBennett Hearsay, Corbitt Sequestration, and Magbanua TestimonyMentioned

Summary

Judge Hankinson sustains the State's hearsay objection barring Sherry Bennett from impeaching Luis Rivera through a Jessica Rodriguez statement, denies the State's request to retain Sergeant Corbitt in the courtroom during Magbanua's testimony, and hears that Magbanua has decided to take the stand in her own defense.

Mentioned in this proceeding.

KMMagbanua RetrialMay 18, 2022 – May 27, 2022

Listed as a defense expert witness, Sawicki was withdrawn before testifying — first flagged as a scheduling uncertainty, then dropped from the witness list entirely without explanation.

Day 6

Day 7