In many court cases there will be more that one defendant being accused of the crime. In some cases, even when the cases are being heard separately, the defendants might tend to able to mount a joint defence to save time and money while building a case. Here are some reasons for and against using a joint defence strategy.
This strategy can save time and money as your lawyers can share resources. This can often work in your favour if you feel like you are being drowned in paperwork from the other side. This also allows smaller defendants to get insights from the larger defendants and more resourced legal team. This usually leads to a stronger legal case for all defendants and can allow you to access additional experts such as expert witnesses to help analyze and defend against prosecution evidence.
As you are working with the other defendants, you cannot mount a defence where you are innocent and they have done the crime, which can make it harder to completely disengage from the crime particularly if there is strong evidence that one or more of you have been involved in the crime. You may also not be able to mount some defences that pass more of the blame onto the other defendants. While operating a joint defense you also need to share all information and strategies which could include distributing personal or confidential information to a wider circle of legal professionals than you have intended. (Legal privilege extends to all of the people in the combined legal team, so you don't need to be concerned about this being disseminated beyond this groups).
While you can mount a joint defense on a verbal agreement, it's best to formulate any such arrangements by drawing up an agreement between the parties showing how information and costs will be shared. This helps to avoid any unpleasant surprises such as very large legal bills down the track and ensures all of the defendants are 'on the same page' as to how the defense will work together.
If you are a co-defendant in a case it can be worth considering a joint defense strategy. While the strategy is not appropriate in all cases it can be a good way to pool resources and conserve funds in a length legal battle. It is worth discussing this possibility with your lawyer early in the process of mounting a defense.