(CNN) -

One of the few details to come out of the murder case against suburban Atlanta dad Justin Ross Harris -- whose son was found dead after being strapped into a hot car for hours -- is that he searched for information about such deaths shortly before the incident occurred.

According to police, Harris used his work computer to search for information about "child deaths inside vehicles and what temperature it needs to be for that to occur."

Police seized Harris' computer as part of their investigation into 22-month-old Cooper Harris' death and included the details in a search warrant affidavit released last week. His wife also searched the topic, police say.

Harris will be in court Thursday for a preliminary hearing on charges of felony murder and child cruelty.

While Harris' family appears to be standing by him and he's been convicted of no wrongdoing, the revelation is the latest reminder that what you do and say online can become public in unpredictable and sometimes undesirable ways:

Digital breadcrumbs are becoming as common in criminal trials as fingerprints

Fifteen or 20 years ago, the notion of taking criminal evidence from a personal computer was as novel as the technology itself. Today, it seems commonplace and all over the headlines.

Last year, for instance, authorities detailed a document called "Abducting and Cooking Kimberly -- A Blueprint," found on the computer of New York cop Gilberto Valle, and made it part of a criminal case against him. A jury convicted him, but last week a judge overturned the verdict, saying Valle's writings appeared to be little more than twisted imaginings.

And then, among the many other examples, there's Casey Anthony. Prosecutors said someone in her parents' home searched for chloroform recipes before Anthony's daughter disappeared in 2008. A jury acquitted Anthony of murder but found her guilty on lesser charges of providing false information to police.

Despite this, people are still posting incriminating things online

Just last month, New York police built a case against dozens of gang members who posted incriminating text and photos to Facebook. Two indictments in the case largely consist of details of Facebook posts in which alleged gang members talk about guns and retribution.

Here's one from the indictments, posted for all to see on the worldwide social network: "AYO, THIS IS BETWEEN ME AND YOU BRO DON'T TELL NOBODY THIS, LISTEN, KEEP IT REAL WITH ME BRO IF YOU REALY WANT TO CLAP, KILL, SHOOT, ONE OF THESE ... I'M WITH IT CAUSE THEY GETTING OUT OF HAND BRO."

Vice News quoted the Rev. Vernon Williams, a neighborhood youth activist, as calling the teens "Facebook dummies."

That's not the only example. Last year, a Florida man allegedly killed his wife, then posted a picture of her body and an apology to Facebook before turning himself in to police.

And then there's Steubenville, Ohio, where two high school athletes were convicted in the rape of a 16-year-old girl chronicled in social media postings.

And they're still getting tricked

The online world is a wonderland of ill intent, with its myriad scams, frauds and trickery. Who could forget Manti Te'o, the college football player whose story of long-distance romance ending in tragedy turned out to be a hoax perpetrated by an admirer?

In June, according to AL.com, authorities charged an Alabama girl after she allegedly tried to enlist a Facebook friend to kidnap her and, if necessary, kill her aunt. Turns out, the "friend" was the aunt, who reportedly had created the fake profile in a bid to keep an eye on her troubled niece.

You should know this: The law is still changing

Yes, police can get a warrant to search your computers -- at home and work, according to the Electronic Frontier Foundation, which has a handy guide to electronic evidence on its website.

The Justice Department also maintains a manual on electronic evidence. It's meant for investigators but covers in detail what can and can't be done legally.

Investigators can even search your computer in limited cases without a warrant -- if they have good reason to think incriminating evidence will be destroyed before they can get a warrant.

Things like photos, documents and search histories on the computer and online are all fair game.

And, as we've seen, they can -- and do -- use information from social media postings. According to a 2012 report commissioned by LexisNexis, four of five police officers reported using social media in investigations.

Not only can investigators get a warrant to look at a secured account directly, a federal judge ruled in 2012 that they're free to find a willing Facebook friend of a suspect and get a look that way.