Both myths on this page share the same underlying error: mistaking a genuinely useful security layer for a complete security system. Neither cameras nor dogs are worthless, and neither is sufficient on its own. Understanding specifically what each does and does not do is what allows a household to build a security plan with no single point of failure.
01 — Do security cameras prevent crime?
Cameras document reliably; whether they deter depends on the crime and the context
The myth
"Cameras prevent crime, so a visible camera is enough to stop a break-in."
The most rigorous available evidence on this question comes from the National Institute of Justice's CrimeSolutions clearinghouse, part of the U.S. Department of Justice, which reviews standardized evaluations and meta-analyses of crime-prevention practices. Its current rating for public surveillance camera systems is "Promising" for reducing overall crime, property crime, and vehicle crime, and "No Effects" for impacting violent crime. That is a meaningfully different claim than "cameras stop crime." A promising rating means the evidence supports a real but limited effect on property-related offenses specifically, not a guarantee against any particular break-in, and not any measurable effect on violent crime at all.
A separate NIJ-funded evaluation of Milwaukee's police-monitored camera program found only limited evidence that the cameras improved case clearances (arrests linked to the crime location), and noted that camera-covered intersections actually recorded more reported crimes after installation than comparison areas, likely because the cameras were catching incidents that would otherwise have gone unreported entirely, rather than preventing them from happening. That finding cuts directly against the assumption that a camera's primary function is prevention. Its most consistently demonstrated function, across the research, is documentation: producing evidence that supports investigation, arrest, and insurance claims after an incident, whether or not the incident itself was deterred.
Separately from the formal research, self-report data from convicted burglars, most notably a University of North Carolina at Charlotte study of more than 400 incarcerated offenders, found that a large majority said they would check for visible security measures, including cameras, before attempting a burglary, and many said they would move to another target if visible security was present. This is real evidence of a deterrent effect on target selection specifically, but it describes what burglars claim they would do when scanning multiple potential targets, not what stops a determined intruder once a specific property has already been chosen and entry is underway.
- NIJ's CrimeSolutions rates camera systems "Promising" for property crime, "No Effects" for violent crime. This is the most rigorous available synthesis of the research and describes a real but bounded effect, not a guarantee.
- Cameras primarily produce evidence, not physical resistance. A camera does not stop a door from opening. It creates a record that supports investigation, prosecution, and insurance claims after the fact.
- Burglar self-report data shows a real effect on target selection, not on stopping an in-progress entry. A visible camera can influence which property an opportunist chooses to target before committing. It does not physically prevent entry once a decision to proceed has been made.
- Physical security is what actually resists entry. Solid-core doors, deadbolts, reinforced strike plates, and secured windows are the layer that determines whether an intruder who is not deterred by a camera can actually get in.
The reality
Cameras primarily document events and support investigation and insurance claims; the research does not support treating them as a physical barrier. They provide a real, evidence-backed deterrent effect on target selection for property crime specifically, with no demonstrated effect on violent crime. Physical security, locks, reinforced doors, and secured windows, is what actually prevents entry once a target has been chosen.
02 — Is a dog a complete security system?
A dog is a considered factor in target selection, not a standalone security layer
The myth
"A dog in the house is all the security a home needs."
The same UNC Charlotte burglar interview study that examined cameras and alarms also asked offenders what signs of increased security they considered when selecting a target, and dogs inside the home were named alongside alarm signs, active alarms, and visible cameras as a factor burglars weigh. That is genuine evidence that a dog changes an opportunist's calculation. It is not evidence that a dog functions as a complete system, and the reasons are structural rather than speculative.
A dog cannot alert anyone outside the home directly. Unlike a monitored alarm or a camera with remote notification, a barking dog only helps if a person, inside the home or close enough to hear, is present to respond to it. A dog is not present every time the household is: it travels with the family on trips, goes to the vet, stays with a sitter, or is simply out for a walk at the moment of an actual attempt, and any of those situations leaves a property with no dog-based deterrent at all despite the household's mental model assuming there is one. A dog's temperament and training also vary; not every dog reliably alerts to an unfamiliar person, and effectiveness depends heavily on the individual animal, not the presence of a dog as a category.
- A dog is one documented factor among several burglars weigh, not a solved problem. Interview research places dogs alongside alarms and cameras as a consideration, not as a superior or sufficient standalone measure.
- A dog cannot contact anyone outside the home. It has no equivalent to a monitored alarm's automatic dispatch or a camera's remote alert; its deterrent value depends entirely on a person being present and able to respond.
- A dog is not always present. Travel, vet visits, walks, and boarding all create windows where the household's assumed deterrent simply is not there, often without the household consciously registering the gap.
- Effectiveness varies by individual animal. Training, temperament, and breed all affect whether a given dog reliably alerts to an unfamiliar presence; "having a dog" is not a uniform security measure the way a deadbolt is.
The reality
A dog is a valuable alert system and a real, evidence-supported deterrent factor in target selection, but it should not be the sole security measure a household relies on. Dogs can be absent, distracted, or simply not present at the moment an attempt occurs, and they cannot independently contact help. Layering a dog with physical security and, where affordable, monitored alerting closes the gaps that a dog alone leaves open.
Quick reference
- NIJ CrimeSolutions rates camera systems "Promising" for property crime, "No Effects" for violent crime. Cameras primarily produce evidence for investigation and insurance claims; physical security is what actually prevents entry.
- Burglar self-report data shows both cameras and dogs influence target selection before an attempt, but neither stops an in-progress entry the way a locked, reinforced door does.
- A dog cannot alert anyone outside the home and is not always present. It is a real deterrent factor, not a standalone system.
- The fix for both myths is the same: layer measures rather than relying on any single one. Physical security, documentation, and human or monitored response each cover a gap the others leave open.
Primary sources
- CrimeSolutions, National Institute of Justice (U.S. Dept. of Justice): Closed Circuit Television (CCTV) Surveillance: the "Promising" rating for reducing overall crime, property crime, and vehicle crime, and the "No Effects" rating for violent crime, based on systematic review and meta-analysis of rigorous evaluations.
- National Institute of Justice: How Do Closed-Circuit Television Cameras Impact Crimes and Clearances? (Milwaukee evaluation): limited evidence that CCTV improved crime clearances, and the finding that camera-covered areas recorded more detected incidents post-installation, consistent with a documentation rather than prevention function.
- UNC Charlotte: "Through the Eyes of a Burglar" (Kuhns et al., 2013): interview data from more than 400 incarcerated burglars, including the finding that dogs inside a home, alongside alarms and cameras, are a considered factor in target selection.