that's a pickle. lying is such a sucky habit, and so distressing. i can hear how worried you are.
but he's only 5, so do keep that in mind. in many ways it seems as if you think he IS 15 or 18 and can reason like an older teen. he can't. he's a very young fellow, and still trying to figure it all out. and btw, older teens don't just lie easily. mine sure didn't.
truthfulness is a habit, and a philosophy. rather than laser focusing on this little fellow's lies, you might start with examining how your family as a whole operates. if you are casual about 'little white lies' you might want to address that. 5 year olds don't get nuance when it comes to honesty. (neither do some 57 year olds, but that's another post.) if he hears you casually 'little white lying' to phone solicitors, or to get out of doing something with someone you're not eager to see, or to get a day off work, or to make (or break) playdates, you're tacitly teaching him to lie.
think less about what punishments to impose for lying and more about setting up his world so that telling the truth is easy and natural, and lying difficult and problematic. don't frown and demand 'did you make that mess in the living room??'
it's almost impossible for a 5 year old NOT to respond that sort of thundercloud with 'no! it was HIM!' and put it off on baby brother.
instead try, 'oh no! the living room is a disaster! we can't have story time until it's cleaned up. come on, let's pitch in together and get it done as quickly as possible.' then as you're picking up the toys, you can casually mention a time when you were a kid and having so much fun you didn't realize what a cyclone you had created. you can invite him into truthfulness with empathy, instead of demanding it with discipline.
and by all the gods and little fishes, no more 'hurt and sad.' he's 5. he's not in charge of your emotions, and it's a terrible burden for parents to lay on the psyches of tiny little people. he should not be able to manipulate your moods, consciously or unconsciously, and even if you ARE so soft and squishy that tiny people can do this to you, you need to project the image of strength and resilience until it becomes real. you need to be calm, and firm, and a place of strength and reliability for him. i know many parents decide it's 'manipulative' of kindergarten age kids to play these games, but i don't see it in the pejorative sense. i see very young people who are not in control of their worlds testing the boundaries, and to their dismay, finding them loose and dangerous. being very young, they keep pushing until they find that solid wall of 'this far and no further' that they desperately need.
give it to him.
but with patience, and understanding, and realizing that a) he's very young and figuring it all out and b) at this point it has become a habit and is very hard to break. this isn't his fault. help him.
khairete
S.