it is the physician's responsibility to obtain consent -- permission from the patient/family to do the procedure. "obtaining consent" includes risk/benefit conseling, descritption of the procedure, etc.
[color=#483d8b]in most institutions, it is the nurse's responsiblity to get the form signed. i did work in one hospital where the surgery residents got the signature on the consent, but usually that is the nurse's job.
[color=#483d8b]in getting/wittnessing the signature, you are verifingy that they are indeed the ones signing the consent, and that they are signing voluntarily, are cognitivly capable of giving consent (are able to understand the risks/benefits) and have been educated on the procedure.
[color=#483d8b]when i get a consent signed, i say "here is the consent for the procedure that dr. smith talked to you about. do you have any other questions that need to be answered before you sign?" if they say they have questions, i answer them if it is appropriate for me to do so (will i come back here after surgery? type questions). if they need to talk to the surgeon again before they sign, then i don't have them sign the consent; i let the sugeon know that they need to talk to the patient again.
[color=#483d8b]granted, the surgeon isn't going to be happy about this; however, that is his/her job. part of the nurse's job is to be sure the consent is an informed one.
[color=#483d8b]when i wittness the consent, i also let them know that they are free to change their mind at any time.