Telling Lies

Is it wrong to lie, or does it depend on the circumstances? There are many different variations of telling lies, ranging from a small lie to protect someones feelings such as when asked "does my bum look big in this" we automatically say "no", even if it does, c but why are those little white lies we all tell acceptable? Whilst researching around this topic i cam across a newspaper article from January 2005, where a mother had lied to protect her son, which at first glance seemed to be a natural thing for a mother to do, except it was to protect her son from being found guilty to murder, which it has now been proven he did commit, but what is the right choice to make when deciding to lie. Do those small 'fibs' we all tell at some point, give us the motive to expand the lies we tell as adults and by doing so especially in the article linked below possible could have prevented justice being served, at what point do we have to draw a line?

http://www.telegraph.co.uk/news/1481697/Lies-to-protect-a-son.html