Crowd Sourcing Gun Control

Background checks deter only those with prior offenses. For more comprehensive gun-violence prevention, we need systems that help law enforcement focus on high-risk individuals before their first offense. Such prevention systems must operate within important legal and political constraints: they must be compatible with the second amendment, they must be relatively effortless for the vast majority of low-risk gun buyers/owners, and they must respect the privacy of all citizens.


Graph theory makes it possible to extract strong information from a large set of weak relationships. It is the foundation of companies like Google and Facebook. It is the basis for alternative metrics that assess the quality of scholarly papers. Graph theory also applies to gun control. As individuals, we absorb all kinds of information about others and decide to like or dislike, befriend or avoid, trust or distrust them. These individual assessments are rather unreliable, but they become a powerful resource when connected with one another in a graph. For gun control, imagine a system in which gun owners recommend one another. This creates a graph on which to unleash the power of graph theory.

Consider a concrete example (no graph-theory knowledge required):

1. Every gun buyer/owner registers three Qualified Recommenders (QRs). Without assuming any legal liability, QRs state that the gun buyer/owner is not presently a danger to himself/herself or to society and that they will withdraw as QR if their opinion changes or if they should lose contact with the gun owner.
2. Most legal gun owners may act as a QR. However, law enforcement may revoke anyone's QR status at any time for any reason. Such action prevents this person from submitting new recommendations, and it voids his/her existing recommendations. Revoking the QR status carries no other consequences. One's own QR status does not affect one's right to own guns.
3. A gun buyer who is unable to obtain three QRs is subject to a background investigation that may include interviews with family, friends, and neighbors.
4. A gun owner may lose recommendations because (1) QRs may withdraw their recommendation, (2) QRs may die, or (3) QRs may lose their QR status. A gun owner who does not maintain three QRs is subject to increased scrutiny.

Maintaining three QRs is relatively effortless for low-risk gun owners, who tend to have strong ties to their communities. If they should become high risk (through mental illness, for example), their QRs are likely to withdraw their recommendations, thereby creating an early warning.

The impact on high-risk gun owners is more substantial. Very few law-abiding gun owners would be willing to sponsor someone they consider dangerous because of mental health, behavioral issues, or criminal connections. Convicted criminals cannot be QRs, because they cannot be legal gun owners. This reduces the pool of available QRs for their non-convicted associates. Law enforcement can reduce that pool even further: when they arrest someone, they could revoke the QR status of the arrestee and of his/her QRs (under the theory that these QRs are unreliable).

Consider a few scenarios.

Scenario 1. Joe is a gun owner. His QRs are his wife (Mary) and two friends (John and Pete).

Scenario 1a. Joe develops a mental-health problem and is in therapy. Mary convinces Joe to dispose of the guns. Mary withdraws her recommendation and, perhaps, approaches John and Pete to withdraw theirs. There are no legal proceedings of any kind.

Scenario 1b. Joe develops a mental-health problem, refuses therapy, and develops violent tendencies. The QRs and the police develop a plan to withdraw their recommendations and, simultaneously, to impound Joe's weapons. After the emergency intervention, Joe's fitness to own guns is evaluated.

Scenario 1c. Joe is arrested under suspicion of committing a violent crime.

Upon his arrest, Joe's QR status is revoked immediately. Joe's gun rights depend on the resolution of the criminal case against him. Mary, John, and Pete are not legally liable for failing to intervene in time, but their QR status is revoked.

Mary, John, and Pete remain legal gun owners. If they acted as each other's QRs, they have to find replacement QRs. For most gun owners, these circumstances are an extremely rare occurrence, and replacing QRs is a low hurdle. For criminal gangs, every arrest eliminates QRs from their environment and increases their difficulty of replacing QRs.

Scenario 2. Bill sells his recommendations. As soon as he is identified as a shady operator, the police subjects his network to heightened scrutiny. With the first arrest in Bill's network, he loses his QR status, and his recommendations are voided. As Bill's clients find replacement QRs, they leave useful network trails.

Scenario 3. Mary, a law-abiding citizen living in a gang-infested neighborhood, wants a gun for protection. Some of her relatives and friends have arrest records, and she cannot find three QRs. She is a high-risk gun buyer because of the circumstances of her life: her gun is at much higher risk to be stolen and/or misused. She is able to buy a gun after passing an in-depth background investigation.

Scenario 4. Bob is a criminal and does not care about gun laws. Because his guns are illegal, he faces a much harsher sentence if arrested and convicted.

Bob's guns are most likely stolen or obtained from sources that claim their guns were stolen or lost. If one of his guns is traced back to Mary, her QR status is revoked immediately. If Mary is an innocent bystander, losing her QR status is no big deal. If she is a member of a network that traffics guns illegally, this incident reduces the pool of available QRs.

Other Scenarios. The QR system implements a form of social control that occurs organically in small communities where everyone knows their neighbors (a rarity nowadays). The process of finding QRs provides opportunities for a community to intervene in a non-confrontational manner and to help prospective gun buyers make a realistic assessment of their own risk profile.

The QR system shows that gun-violence prevention does not require storing detailed personal information. It shows that an alert and involved community does not need to become a society of snoops that report every eccentricity to the police. Yet, the QR system is just one example. Graph theory provides a lot of flexibility to respond to legal and political concerns.

I call on the graph-theory community to contribute to the gun-control effort. It is up to you. Criticize. Amend. Propose. Do something. Anything. Save lives.