Being through the justice system several times I can tell you. You can be arrested for anything here in the USA and their may and may may not be a bail. I was arrested for felony stalking, the case was thrown out but only after I spent a thousand on bail and another thousand on an attorney.
Can a person be demanded to pay bail if there's very little evidence against him in a serious crime, such as murder?
If you are arrested and they set bail, then you have to pay it to get out. Whether there is enough evidence or if you are even guilty or not has nothing to do with the bail process. That is what criminal court is for.