Whenever someone (who is not, essentially, in a wheelchair) is raped or killed without witnesses to the whole crime, "reasonable doubt" enters the picture. Under American justice, no unwitnessed violent crime can ever achieve certainty "beyond a reasonable doubt" unless the perpetrator assists in her or his own conviction.
Juries can conclude that someone is guilty beyond a reasonable doubt, but they're never correct, legally, even if they're correct in a moral, ethical, or factual sense. It is always possibly that the rapist's story "she wanted it, and she wanted it rough, and she was holding the candlestick over her throat because she's a gasper" is true. Similarly, it's always possible that the murderer's story "he suddenly attacked me so I had to shoot him" is correct. Barring the rape victim having been diagnosed brain-dead, or the murder victim having been brain-dead, paraplegic, comatose, wheelchair-bound, or something similar, there is always a logical, rational, potential reasonable doubt.
"Reasonable doubt," then, tends to be equivalent to middle-school student council elections in rationality, in that one person's reasonable is never another's. The social standards of any time period, coupled with a thousand other things, chief among them the wacko opinions of any given judge or jury member (or jury/media/attorney/sequestration-hotel dynamic), determine how "reasonable" any doubt can be.
Because the girl really could have been a gasper, asking for her larynx to be smashed, or the boy really could have suddenly attacked a bigger man out of nowhere. There is always reasonable doubt; there is always a reasonable way to construct any narrative, and only varying sets of prejudices that will inform different groups as to which parts of an explanation are reasonable, and which not.
The only way to overcome the hypothetical standard is to treat it as a sham, and so it is: because there is always reasonable doubt, cops and prosecutors trick perpetrators into giving themselves away by unsettling them, questioning them, repeating things, scaring them with legions of potential indictments to curry easier plea-bargains, and, if that all fails, actually holding a trial where jurors can convict anyone they don't like. In the rare circumstance where "reasonable doubt" actually has an impact on a case, it's when the accused is lucky enough, or perpetrator clever enough, to have (1) a jury who "likes" them for some unfathomable and inappropriate reason, or (2) a jury that is stupid enough to actually apply reasonable doubt (e.g., a jury that can't possibly convict, because there is always reasonable doubt).
There was reasonable doubt for O.J. The LAPD probably did attempt to frame him, but even when they'd blundered through all of it, he was still the one who'd committed the murder. Nonetheless, there was reasonable doubt, because the LAPD could have planted even the evidence that they hadn't actually planted (if they'd had an extra several secret agents working on the case).
The Fairness and Unfairness of Reasonable Doubt
Reasonable doubt is always there, and it's appealing as a legal concept because, if actually applied, it would prevent all innocent people from being convicted, prevent all victimless crimes from being enforced, and end the American police state. It's reasonable to assume that someone planted the marijuana in your backpack while you were getting change for the subway--hundreds of people a minute pass by that point, and any one of them could've seen the transit cop before you did, and tried to get rid of the stuff so as to avoid arrest. It's reasonable to assume that any murder victim could've started the fight with a deadly weapon, surprised or overpowered you, and necessitated the murder (especially if you have time to rough yourself up a little afterwards).
Reasonable doubt seems fair because it prevents you from being convicted (in theory) only on "circumstantial" evidence. Pursuant to circumstantial evidence, anyone at the scene of a murder could be guilty, because they all lived and the victim died. Pursuant to circumstantial evidence, any sex could be rape after either partner changed his or her mind; any sparring match could be a violent assault. There are innumerable ways, gone into in great detail in mid 20th century American cinema, about how circumstances can make it appear that someone was obviously guilty, even though they're actually (and also obviously) not. Circumstantial evidence is a terrible deciding factor; it's what Obama's handlers use to blow up ten thousand kiddies, because they lived across the street from someone who might've once visited a part of Pakistan that could've been controlled by the Taliban during that time period if anyone had been there to witness it who was trustworthy (actually, even Obama stretches circumstances to several leagues beyond the breaking point, but you get the idea).
Circumstantial evidence, clearly, sucks. But then, so does reasonable doubt, because reasonable doubt gets everyone off. Any rapist, ever, could claim "she wanted it," and that could be true--females do have sex drives. They are not all chaste Christian virgins who have sex three times in their life to conceive three children, as hard as that may have been for the children of the Puritans to accept. Reasonable doubt gets all rapists off, unless they're stupid enough (or frightened enough) to confess, which is why reasonable doubt got thrown out the window in rape prosecutions where the rapist does not make a huge, graphic mistake, like (1) break down sobbing and ask the cops if he can just get probation if he confesses, or (2) claim the sex didn't happen at all, forgetting about physical evidence. And reasonable doubt, of course, can justify why O.J. and Zimmerman were not convicted. There was reasonable doubt, even though both of those men killed the people they were accused of; there is always reasonable doubt (unless you're one of the targeted minorities, crimen-exceptum "committers," or foolish early-bargainers).
So, reasonable doubt sucks as a standard, too. If it were applied, judges would throw out almost every criminal case, prosecutors and cops would be prevented from cutting bargains with hapless accused by tricking them into not asking for a lawyer despite Miranda, and that would be that for the criminal law. Nine guilty men would go free so that one innocent man would not be punished, and so forth.
If you're a fan of "reasonable doubt," and of trial results where a killer is not punished by virtue of an explanatory story, then you have to be ready to accept a world where any non-witnessed, non-wheelchair killings are assumed to be self defense--and the crime of non-witnessed rape vanishes. In short, if you support defenses of "reasonable doubt," then you're in favor of all-male juries watching as a male lawyer asks "reasonable" questions about a raped secretary's past sexual relationships, to establish that she did, in fact, "want it." And you're probably not in favor of that, right? To accept that females have (1) a sex drive, that (2) all the details of that sex drive shouldn't be made public, that (3) all humans may make their own decisions, including changing their minds about what they want at any point they damn well please, and (4) it is not your personal right to decide what another person was thinking at any given time, you have to, resultingly, accept that any person (including the stereotypical woman) could want sex, later decide she didn't, and make a false accusation. That's "reasonable doubt."
If you're a fan of "circumstantial evidence," and of people being convicted simply because they were the only person discovered (or proved by physical evidence) at a crime scene, then you have to, essentially, approve of Guantanamo Bay. Living in the neighborhood where five rusted old AK-47s are being stored in a basement could, indeed, be the hallmark of a terrorist mastermind planning to destroy America. Sharing a college dormitory room with a girl who is gang-raped by the rugby squad could indicate a conspiracy to unlock the door late at night, witness the rape, and use the incident to ruin your girlfriend's reputation. Waking up in a room next to a dead person means that you killed that person, etc.
Circumstantial evidence is an abjectly terrible standard, which is why "reasonable doubt" seemed so appealing, in theory. Neither standard is very good, though; the history of the Tower of London, roughly, suffices to demonstrate why arbitrary and/or circumstantial "evidence" is not good, while a hundred years of African American conviction rates either (1) proves the Bell Curve or (2) demonstrates that "reasonable doubt" is a really stupid, shifting popularity contest that only gets pranced out when it's time to let some murderer go free because the jury found Latin impressive.
Let Me Just Ask Mama
Human societies used to deal with this kind of crap in a much easier way. This is a shocker to feminists and neo-feminists, because it recalls, essentially, Jane Austen. The moral of the story was, if you don't want to get murdered or raped, stay in safe places.
It seems simple, and it was. It was part of the surviving kinship network of human society, still hanging on until industrialism finally fractured it the rest of the way. By living with a large group of people who knew you, you were protected from the kind of casual, constant, intra-society violence that characterizes the modern state. Young men were considered troublesome rogues (and not in a funny, romance-novel kind of way, but a serious, "asshole" way) when they roamed around, unsupervised, looking for trouble. "Dates" occurred by chaperone, making "date rape" (and rape in general) nonexistent, until the enclosure of the commons and the factory system turned clans and tribes into isolated "families," where husbands could reign, unwatched, over wives and children. Whacking people in front of a group, or where women and children had a network of aunts or cousins or grandfathers to turn to every day, was not so easy.
(Young men and women had the freedom to do whatever they liked, of course--to disobey would've meant losing social standing. So, people were more free, in the sense that they could follow their hearts, if they were willing to risk unpopularity (or having people worry about them), but not receive official state censure and imprisonment. The "reduction" in freedom was illusory; the restrictions were based on unpopularity, rather than police force. It wasn't a paradise, it wasn't perfect, and it shouldn't be "returned to"--just food for thought.)
The old-style "patriarchy" that industrial feminists destroyed, they destroyed on behalf of factory owners, who wanted poor women and children (and men) to be able to walk through the streets by themselves to go to work--where they would be isolated, left to the mercy of foremen and their lords, for beating, pleasure, or both. The isolated individual making a "trip to work" became the prey for Jack the Ripper, and the other urban legends (yes, "urban" for a reason) spawned by the breakdown of what was protecting poor people: namely, other poor people. Fathers would have once kept daughters from being raped in the street by accompanying them on walks, or insisting that they go with friends. Factory owners, though, needed shifts scheduled by the clock, rather than by human time. They thereby created accessible resources that would inevitably draw predators.
The easy counter to this is "well, there was abuse before," and there was--but it was not, primarily, the covetous, propertized, secret abuse of the modern family. Under the eyes of all, the standards differ. You would expect a violent man to rape a woman in a dark alley, or perhaps in a gang in a shady pool hall filled with other violent and/or frightened men--but would he be able to do it in front of the local PTA, or another equally-representative slice of the populace? Communal living protected people. Kin, clanswomen, or tribal brothers would travel in groups, protecting each other, and making the price for inter-group violence higher--if another clan had to attack eight people, instead of one, the common story would be clear, and it would be a feud. If only one person vanished, or two people had a fight and disagreed, stories would conflict much easier.
The modern "court," overseen by a lord or king, is a creature of the increasingly isolationist society of industrialism and post-industrialism. If "everyone" sees a crime happen, there is no attempt to lie about the details of the event itself. The perpetrator (or both of them) may try to claim the justification of past grudges, but the tranquility of the group--which cannot afford that kind of bullshit, if the group is to survive--forces the grudges and stories back down. Revenge murder drops; years of hidden spousal abuse drops; panicked women stop drowning their children in the river, because other caretakers are around.
Cops and prosecutors now railroad people through the system because they know that "the system" is too cumbersome, if actually employed the way it was written, to accomplish anything. Savvy or lucky perpetrators can get away with a lot by employing that system, and there will always be plausible deniability. Even in the face of constant, total, electronic coverage of everything, infiltrators of the records ("hackers") will create the same problems that now exist between circumstantial evidence and reasonable doubts.
The human solution is living together. Being meant to live together, humans will not only benefit from the removal of most need for abstruse, ridiculous, courtly rituals of how things happened, or the heartless, doubtless quota-punishment crusades of the plea bargain and coerced confession; they will also benefit by a vast reduction in the antisocial illnesses that develop from living apart, which result in the post-industrial crimes that so befuddle the post-industrial method for dealing with them. In very plain, currently-popular terms, violent idiots like George Zimmerman are created by individualized family-units, single-family residences, gated communities, and all the rest of the western crap. And, as long as they can iron out the contradictions in their narrative within a week or so, groups of intelligent, naive fools who believe in the rules will be forced to exonerate them.
If you wish--and only if you wish--prehensive individual planning, prior to some manner of mass social decency, would be to follow more "traditional" routes to safety. You certainly have the "right" and the "freedom" to go anywhere you please, and it is the bane of post-industrial materialism that you might not be able to (1) work or (2) shop at any time and place in the world. If you look forward to vigilante encounters, different advice is your forte; if you don't, then there's no need to be shy, or feel sexist, about giving or following the same tips that any security professional will lecture on to a roomful of well-built male personal trainers or nightclub bouncers.