BRENTWOOD -- If you're going to give your kids a weapon, make sure they use it very, very carefully.
"That's exactly how we have to treat (cellphones)," Brentwood police Detective Mike Thompson said Tuesday in a frank presentation about the potentially dangerous -- even deadly -- relationship between mobile devices and social media.
About five dozen parents gathered at Heritage High School to hear Thompson deliver an adult-oriented version of the message that students on the Brentwood campus had heard the week before.
With expertise in computer forensics and handling Internet crimes against children, Thompson offered a liberal helping of warnings and advice borne of his own experience as the father of a teenage girl.
To underscore the importance of parents paying attention to their child's cellphone habits, he rattled off facts bordering on the absurd: Children as young as 8 are using social media an average of 7½ hours per day, and the typical teen sends an average of 3,339 texts per month.
In light of those numbers, parents who don't keep a close eye on what their child is up to are inviting trouble, Thompson said.
That goes not only for cyberbullying, but sharing the wrong kind of personal information online or communicating with strangers who might not be who they seem, he said.
For example, unless teens know how to manipulate the privacy settings on their smartphones, the latitude and longitude coordinates embedded in photos they text or post can enable someone to see exactly where they are, Thompson said.
And if a young person offers up too much online during a family vacation, he or she is alerting burglars that the house is unoccupied, he added.
Thompson also briefly introduced parents to software applications ranging from Snapchat and WeChat to Vine that many teens currently are downloading to their phones.
He urged them to remind their children that whatever they write or display online remains on the Internet even if they later try to delete it.
They have opened a Pandora's box with the compromising photo or cruel rumor they posted, which can travel like wildfire among social networks as their friends share it with others, Thompson said.
To drive his point home, he showed a video about Jill Naber, a 15-year-old Los Gatos High School freshman who hanged herself in 2009 after the topless "selfie" she had sent to a boy ended up on the Internet.
"We had no idea (that the photo existed)," said Polly Naber as she and her husband recalled their daughter's suffering.
And although kids use Snapchat to send videos that disappear from the recipient's phone after a few seconds, Thompson said the feature might give some a false sense of security; there's nothing preventing someone person from taking a photo of the on-screen action -- thereby capturing a permanent record.
Youthful indiscretions can come back to haunt the young person when college admissions officers and potential employers turn to the Internet to learn more about them, Thompson said.
These days those missteps also can be a criminal offense: He noted that both the underage sender and recipient of nude personal photos are violating child pornography laws. And a new law written with social media in mind makes it illegal for individuals of any age to share such an image without the permission of the person in the photo.
The Brentwood Police Department held the talk in conjunction with the Liberty Union High School District, which plans to organize the same event for Liberty High School students and parents. The district also intends to work with the Oakley Police Department to provide a presentation to the Freedom High School community.
Reach Rowena Coetsee at 925-779-7141. Follow her at Twitter.com/RowenaCoetsee.
Here's some advice that Detective Mike Thompson of the Brentwood Police Department has for parents of kids with cellphones:
-- Rowena Coetsee