Always believe the creepy guy you just met over your best friend.

WILDCHRISSY32
it's true he lied to them before but that was always more out of fear then an outright desire to deceive people and mess with their lives. The first lie he told technically speaking was when he said he killed his aunt which is actually the one I sort of understood because he was terrified and in shock and he loved his father so he wanted to protect him. When he came back 5 years later after being in juvie and going through God only knows what kind of messed up stuff he is just starting to try to get back some semblance of normalcy and Regina gets killed and he finds his aunts necklace that Regina had for some reason that was never answered in his locker. Which leads us to the second lie which again stems from fear of what will happen because when it's mentioned that he could go to real jail this time you can see the fear in his eyes. Then he finally tells the truth about Aunt Tara and the necklace. When he does though you can tell how scared and vulnerable he is and it only makes him being in juvie worse because he was an innocent 11 year-old boy probably surrounded by bigger, and more dangerous boys.
Then Charlie appears while he's on the run and he accidentally kills his dad while protecting Jo which leads to the last couple of lies. The first being that he doesn't tell Jo or Lacey right away that he knew Charlie in Juvie which while not technically a lie was in fact a dangerous omission b/c both girls would have stayed away from him if they had known the truth. The last lie was lying about the accident that killed Vikram but again that was fear and that lie and everything that Charlie was doing to screw with him was causing him to unravel a bit.
To be fair though Danny was definitely not the only liar on the show. Tess lied about knowing Vikram was alive and she lied about having another child although again more omission then lie. Jack and Whitney both lied about a whole bunch of crap that we never got answers to, so every one of them had their flaws Danny just had more darkness because of what he'd been through.