In Canada victims do not get to drop charges against an accused. However, what they say may influence a prosecutor.
Prosecutors withdraw charges when they feel that prosecuting is not in the public interest or that there is no reasonable chance of getting a guilty verdict. Different prosecutors in different cases and places will have their own view of what is in the public interest. They also differ on whether or not they feel there is a chance of getting a guilty verdict. As a criminal defence lawyer, the most common way I have seen charges withdrawn in domestic assault cases by recants. If you are considering recanting as statement should seek independent legal advice. If you provide a false statement to the police you can be charged.
If you are charged with a domestic offence you will likely be under a no contact order with the victim. It may be a crime to pressure a victim into writing a recant letter on your behalf. You can be charged with obstruction of justice as well as breaching a no contact order.
Sometimes victims of crimes for one reason or another do not show up for trial. Depending on the reason the prosecutor might drop the charge. If the victim was given a subpoena, a prosecutor may ask a judge to issue a warrant to have the victim arrested and brought to court.
Some victims who are forced to testify at trial sometimes forget what happened and are not sure if they were being truthful in their statements. This forgetfulness can be due to many things. Sometimes the victim was drunk, high or both. Other times the victim suffers from mental health issues or memory problems. Still other times the trauma of the situation has caused the victim to be unable to properly recall what happened. In cases like this where there is not enough evidence to prosecute and it is unlikely that there will be a guilty verdict a prosecutor will drop the domestic assault charges.
Regardless of what happens, it is always a crime to lie under oath and anyone unsure of how to testify at a trial should always seek independent legal advice
The best way to get you charges dropped is to be represented by a criminal defence lawyer who can meet with a prosecutor and discuss why your charges should be withdrawn with the prosecutor. Each case is unique and domestic assault law can be complex. If your full side of the story is presented to the prosecutor by a criminal lawyer who knows the law, this can help you in getting your domestic violence charges dropped. Also, providing evidence of unique circumstances relating to the victim or the relationship can lead a prosecutor to conclude that it is not in the public interest to prosecute. This will ultimately save you the risk of going to trial and potentially getting a criminal record or a jail sentence