Mini Cellphones in Prisons

The respected US trade magazine Security Management devotes its March issue to a threat. It increasingly occupies Europe's correctional facilities. The subject is miniature cellphones. They are so small that they can be hidden in body cavities. DTI managing director Andre Günther was interviewed as an industry expert for the article.

Anyone who works on security in correctional facilities knows this principle. Control over the communication between the inside and the outside world is a cornerstone of the system. Inmates make calls over monitored lines. Visits take place under supervision. Mail is read. All of this works as long as no uncontrolled phone comes into play.

That is exactly what has happened more and more often over the past few years. Miniature cellphones can now be ordered on Amazon or Alibaba for a few euros. Some are barely larger than a lighter. They fit into a closed fist, into a shoe, and, as unpleasant as that sounds, into body cavities. There, no conventional walk-through detector picks them up. The amount of metal inside is simply too small. It does not stand out from the noise of a human body.

The problem is not a marginal phenomenon. It is a serious security risk for all of Europe. The trade magazine Security Management examines it in its March 2026 issue. The publisher is ASIS International, the largest professional association for security management worldwide. The author, Megan Gates, traces how organised crime keeps its business running from inside the cell. Her article carries the title "A Small but Mighty Problem: Tracking Down Mini Cellphones in Prisons".

Europol warns that criminal networks operate from custody

The scale that Gates describes is alarming. In its 2025 threat assessment, Europol notes something new. The remote control of criminal operations from prison cells has reached a new level. Criminal leaders issue orders from the inside. It involves drug deliveries, arms deals and, in the documented extreme case, contract killings. One leader of a Balkan group coordinated his entire network by miniature phone from his cell. Europol had listed him as a high-value target. After his release in 2024, he is said to have had a witness in an ongoing court case professionally eliminated.

In France, the situation escalated. In May 2025 the authorities launched "Opération Prison Break". They searched 66 detention facilities at once and combed almost 500 cells. They seized 164 phones, 88 of them miniature devices. In parallel, the investigators shut down the French online retailer OPORTIK. Around 5,000 miniature phones had entered circulation through that channel.

The technical dilemma

For the technical background, Security Management consulted me, among others, as managing director of DTI Security. The core of the problem is quickly explained. Conventional walk-through detectors were designed for weapons, for pistols, knives and metal tools. A miniature phone contains so little metal that it stays below the alarm threshold. Turn the sensitivity up high enough and the detector reacts to belt buckles, trouser buttons and zips. The false-alarm rate then brings operations to a virtual standstill.

"The amount of metal in these small devices is extremely low. That makes detection with conventional metal detectors much harder."Andre Günther, managing director of DTI Security, in Security Management Magazine

Alternative technologies solve the problem only to a limited degree. X-ray body scanners do make the devices visible. They work with ionising radiation, however. In daily use on visitors and staff, that is a health risk. For pregnant women it is ruled out anyway. Millimetre-wave scanners are familiar from airports. They scan the surface of the body. Objects in body cavities or deep skin folds go undetected. For the use case "mini phone in a correctional facility" they are therefore unsuitable.

66 zones make the difference

The technical answer came over the past two years. A new generation of walk-through detectors works with 66 independent detection zones. Behind it lies not raw sensitivity but intelligent localisation. The detector does not just report alarm or no alarm, it shows the security staff on a body graphic where exactly the suspicious object sits. In this way it tells a belt buckle at hip height apart from a miniature phone in a body cavity.

How effective this is, is shown by a documented case from Germany. One correctional facility had struggled with the same problem for years, because its existing detector only picked up mini phones when it triggered a false alarm on every second visitor. In a one-week trial with a 66-zone detector, the staff then seized around a dozen miniature phones, hidden on visitors and inmates, some inside the mouth. The facility then ordered ten units.

One advantage over X-ray technology weighs heavily. These detectors work without ionising radiation and are therefore suitable for use several times a day on the same group of people, as everyday custody operations require. For pregnant women and people with a pacemaker, walking through at a steady pace is considered safe, and anyone who is unsure can request a hand search.

The underestimated second line of defence

One point also comes up in the Security Management article. As a consultant, it matters a great deal to me. The entrance of a correctional facility is not the only place for a walk-through detector. In practice, cellphones do not only come in through visitors. They also come in through internal routes. The prison laundry counts as a classic smuggling channel. The transitions to the workshop areas are just as critical. Inmates there work with metal tools. Those tools must not reach other areas as weapons.

A well-thought-out security concept therefore distributes walk-through detectors across several critical points, not only at the main entrance. At many facilities this idea has not yet arrived. At DTI we raise it regularly in our consulting.

France draws the consequences

The political level now takes the topic seriously. The developments in France show this. In July 2025 justice minister Gérald Darmanin moved a hundred inmates to the high-security facility Vendin-le-Vieil. Its wing for fighting organised crime is equipped with cellphone jammers and drone defence. Glass partitions were added in the visiting rooms. They prevent the physical handover of objects.

In November 2025 Darmanin went further still. He announced his "zero cellphone plan" for six French prisons. Among them is the storied Paris prison La Santé. The facilities are to receive new security airlocks, millimetre-wave scanners and jammers. The exercise yards will also be roofed over, against phones being thrown in. This is to be completed by 2026.

What this means for the German market

Germany faces the same challenges. The devices keep getting smaller. Online retail makes them available to anyone. Organised crime exploits every technological gap. The article in Security Management Magazine makes one thing clear. The answer does not lie in a single technology but in a combination. Highly sensitive detection technology stands at several checkpoints. Signal jammers and structural measures complement it.

For this survey, ASIS International also looked to Germany. DTI was drawn in as a discussion partner. We see this as confirmation of our work in this segment. We have advised correctional facilities and public authorities for years. It is about the selection, the positioning and the operation of security airlocks. That is exactly the practical knowledge the magazine sought for its article.

Referenced in the article

Garrett Paragon: 66-zone walk-through detector with mini-phone discrimination

The walk-through detector with 66 pinpoint detection zones described in Security Management Magazine. At a German correctional facility it seized around a dozen miniature phones within a week. Radiation-free, IP65-certified, designed for continuous use in custody.‍

Technical details & data sheet

‍Consulting for correctional-facility projects
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Source: Megan Gates, "A Small but Mighty Problem: Tracking Down Mini Cellphones in Prisons", Security Management Magazine, ASIS International, 16 March 2026.

‍Full article on asisonline.org

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