The worst thing about mobile phone technology is how it now has multiple ways in which it reveals your activities. Law enforcement is rather sophisticated with respect to mining the information on phones and the creation of fusion centers has  added to social knowledge sharing within the law enforcement community.

Of course there is always a backlog and forensics on phones isn't a free for all - so you have to be fairly important to warrant analysis such as being newsworthy or useful as a cog or informant or promotional vehicle for the arresting officers.   But do not mistake the security of deleting information on phone or the ease by which it can be retrieved. It is ALL there, stored in the solid state components of your phone.  This is not widely known but you can quickly verify this with few searches.

What is more is that cell tower pings which are now stored much longer than in the past can recreate your activity even with gps turned off.

You imei information tracks your phone even with a new sim in it and the imei information can be and has been linked to the UPC of the phone and this reveals where the phone was sold and can reveal the credit card used to buy it.

The udid on the also provides information that can be linked to the owner or registration information.

If the phone has wireless or data features ... iPhones, androids, blackberries and so on, every ip address visited is now likely to be logged and those logs are now typical stored for two years because carriers are preparing to comply with what maybe become a data retention law.  They already store all numbers called and received for two years as this is a law.  

They are required to keep financial records associated with payment of the service as well.

So it boils down to this everything about the phone can tell me an incredible amount about you even if you erase all numbers and contacts and flush your browser and Mail and text.

This ruling is one of the most dangerous I have ever seen in terms of the 4th amendment rights. But thanks to national security letters, and the patriot act and fear of terror, we have decided to give our rights away. Thomas Jefferson is rolling in his grave and Ben Franklin and Thomas Henry are crying.

You have a few options for privacy: encryption of the phone (but do your research as much of it is baloney) or secure wiping utilities ( for example iwipe) and 3rd party applications that limit or encrypt messages.

The sad news is that your laptop is just as bad but that is still some what protected and tools like true crypt and eraser help there... Although recent evidence suggests even the open source software community has informants now working as developers in area of privacy and encryption.  Note for several years major antivirus and OS companies have allowed backdoors for national security.  Thanks to an explosion in national funding for law enforcement we nown have fusion centers and a whole mass of folks who need arrests, convictions and plots to get raises and justify their existence.

So expect the paranoia to continue and the private industry to create some really cool forensics tools for watching you because the operative words this year are HUMAN TRAFFIC and Terrorist plot and LEAk.... there are bogey men in every bathroom using cell phones and meanwhile Osama is still missing.  Thank you Big Brother.
Uuid on

Re read the paragraph concerning a locked phone. Of course, deleting is preferred, but it appears you can refuse to unlock your phone if asked by the police.

Both reasonable options but not foolproof.  It depends on the application containers which may allocate space that would not be overwritten by a large file. IPhone current gen encryption is good but has two weaknesses - needs a complex password and backups can be hacked and or brute force attacked if your laptop is in custody.

But the real point is these devices can hold a lot of personal information.  Allowing warrantless seizure is unjust and takes your information away indefinitely.  If you don't have much data, not much to fear... But if you have sensitive material do not assume simple deletes take of things.  

I am not advocating paranoia but I am suggesting all is not as it appears.  Imagine someone store important contacts on a phone and the law decides they want the phone.  They capture it, put it in a faraday bag, clone it and then begin to run tools that can use brute force attacks against the encryption (works on older models well) or in the case of phone with deleted files, they can run forensics to restore the original contents.  They call also pull carrier records.  Is this likely to happen.... No.  Can they, yes and maybe.  

We are entering an age where sophisticated private companies can make big bucks selling tools that can mine your lives in ways imagined by George Orwell.  These tools get better every year.  Since privacy is evolving, if you do something wider society publicly condemns you should take care to keep your life private and these days that means being very careful with anything electronic because the Miranda law does not protect you against your written words.  They are stored in silicon and can and will be used against you...  

But I repeat .... The average Joe wanting mobile privacy should buy and destroy phones every few months or send the used ones to GIs overseas after wiping.  Someone with more serious info should get a phone that supports encryption and firewalling (when possible)

For more resources see: eff.org, epic.org, tor.org, ACLU.org, openvpn, etc.  You have a right to your property and privacy.  We cannot let fear of Islamic cells be an excuse to give up our rights ... The ones that make this nation (USA) one of the best in the world.  So as long as they may invade your world, feel free to explore safe guards.

Live free not paranoid, and proper safe guards may save your life because these days with google merely being accused, arrested or questioned can destroy one,s life.

Good thinking...  over-write the deleted data!