Answer: Usually is considered public which is related to a structure of the public domain, such as: school, company, university, administration, newspaper, mass media in general, and those happenings inside of those who are wanted to be made public, for example ‘the 50 years of company alfa celebration’.
Usually, information related to those are of the public domain and falsification considered illegal. Thus: name, date of birth, nationality, place of birth, education degree, working place, status, etc. Changes of name have to be legally registered (artistic name, religious name, etc. and do usually appear on passports or other documents). Thus the marital status, children, etc.
Mass media, and other organs of information divulgation have to consider those before publishing information, otherwise they can sued for ‘divulgation of false information, difamation’ and other.
All the rest is of the private space. Except if confronted to authority in official charge, the subject has usually the right to hide away some of the above mentioned data, though not to falsify them, as there may be accusation of ‘induction into error in order to take an advantage’ (if I say, for example, I’m Robert Redford). Often though, you may make jokes with official data, if it is in private sphere and has no implications.
What is not of the public domain, the subject has the right to hide away even to officials in charge, thus, what is of his/her affective life, personal convictions, thoughts, personal relationships, etc. In some countries it is of right even not to reveal evidences or facts that may have as implication the conviction of crime (France, Spain, Greece), in others though, you may be accused of ‘covering a crime’ (Germany, I think also USA). In Greece this right is respected to the point that the accused is not obliged to swear to say the truth as … he may lie, which is not the case for the one who accuses or the witness.
Nothing that concerns the private space is allowed to be published without the explicit permission of the subject in question. Data concerning health (psychic illness, pshysical illness, addiction to drugs or alcohol) are considered ‘medical secrets’ and are forbidden to be divulgated, except if the subjects does so by himself. Thus also the judicial past of a subject in most countries or the name of someone who has not been judged ‘presumed innocent’ is still a ruling principle in most said civilized countries.
Usually rules concerning a further understanding of the public and the private, vary, if you consider that the public space is any where you may meet other people, a street, a bar, a shop, etc. and the private, the 4 walls where you may be alone. Usually, you are not allow a certain number of things in public which are allowed in a private space, thus expressions of anger and fury, of love and dispair are confined to the four walls without implications (except if infringing laws concerning the use of violence or other illegal acts, specifically ruling sexual behaviour), but you may, normally, even throw a vase against the wall in fury at home, which may be sued in a public space.
This classical distinction suffers of the illegal invasion of the private space by agents of police and others in our modern times, which provokes gravest ambiguities even while considering a supposed criminal subject. Because I may say in anger to a friend ‘I’ll bomb them all up’ without having the slightest intention of doing so, or ‘I’ll kill him, I swear’, without intentionality, and though it may be misunderstood. The violation of the private space may induce the thought of guilt where there is none, such as recordings and other (letters, phone calls) as it is very difficult to say, to which extent a subject is not pretending, lying, giving in to pressure, or just boasting or making fun.
Thus, one day, I said to someone while coming back from changing a pay cheque, that ‘I had robbed out a bank’, while I had just very peacefully gone to a bank. If this is listened do, can you take it seriously? Although these proofs are usually not to be considered, for these reasons, as proofs for justice, they usually conform an idea that may influence a judge’s decision, and this is distorting obviously the normal functioning of justice.