This is an excerpt from reporter Scott Johnson's blog, which focuses on the effects of violence and trauma on the community. Go to www.oaklandeffect.com for updates on his reporting.

Several months ago, I was talking to an Oakland police officer on the telephone, discussing a particular homicide investigation, when the conversation turned broad. Part of the problem with Oakland's violence, he speculated, was that there were several individuals in the city who were incredibly violent, so violent, in fact, that they were essentially psychopaths.

And these individuals, furthermore, were driving the mechanics of death by virtue of their relentless and amoral approach to self-aggrandizement. In other words, their lack of empathy, compassion and any sense of the value of others, compounded with a lack of compunction about killing to obtain what they desired, created a uniquely violent character, a threat to society that went largely unnoticed.

At the time, I thought this was a little extreme. After all, true psychopaths are relatively rare, and truly violent ones rarer still. And the dynamics of violence are so complex that introducing severe personality disorders as a catch-call explanation seemed simplistic and fanciful.

Violence is often a result of robbery, for instance, which in turn can be tied to conditions of poverty, low socio-economic status or substance abuse, which is a diagnosable medical condition. The point is, violence is, I think, best thought of as the result of a web of interconnected problems, none of which are easy to fix, and all of which require subtle changes in perception and understanding.

That said, the policeman's comment has stuck with me over these months, and I've had occasion to rethink its validity. For starters, science is increasingly showing us that repeated exposure to violence -- whether it's gang-related, domestic abuse, psychological torture, maternal separation or substance abuse -- has the long-term effect of dulling and in some cases eliminating the trait of empathy. This is key. Empathy is paramount to socialization, understanding social cues, conversing and communicating with others. It is one of the things that makes us most human. Conversely, a lack of empathy, or a dulled and stunted sense of empathy, is a crippling handicap, as well as a pretty good marker of someone bearing the traits of a psychopath.

Empathy grows and prospers with healthy social networks. We use it to connect with other people, to learn their desires, to feel their pains, sorrows, joys and love. Without these social networks, without caring adults to show us what empathy looks like, there is no room for this particular quality to grow. In other words, it does not sprout up on its own, nor does it prosper if environmental conditions conspire to quash it. And it is a vicious cycle. Where empathy does not grow, its lack is keenly and often violently felt. I can think of no better example than an individual who chooses to shoot into crowds of people in the hope that an intended target will be hit. The willingness to do this -- the ability to contemplate it seriously -- shows a certain lack of empathy. There is no concern for innocent people who might get hit; they are simply there, almost like objects that stand in the way.

Time and again, I talk to older people from Oakland who say to me: It was not like that in my time. Often, these people are former gangsters, criminals, con-men and so forth. They say: In my time, you took care if you were going after someone, you did not allow innocent people to get caught up in your own violence.

This is a marked societal shift about which the city continues to fret, as it should. What to do? How to contain a societal trend in which individuals and groups of individuals, in larger and larger numbers, are willing to spray bullets into crowds of innocent people. In a sense, this is a gun issue, yes. But it is also something else. It is an empathy issue. And empathy grows from the ground up, from families, communities, churches, parents and friends. It cannot be legislated, nor should it. But it can be taught, which is what I think everyone should be trying to do.

Contact Scott Johnson at 510-208-6429 or scjohnson@bayareanewsgroup.com.