The apostle John reminded his readers in 1 John 1:2 that they had an advocate in heaven representing them continually. We know that the only people who need advocates are wrongdoers or those falsely accused of wrongdoing. No doubt there were Christians in both categories among John’s readers and no doubt there would have been a variety of accusers, depending upon where the accusations were being made.
The context in which John’s words are found indicates that the accusations were made in heaven, which would suggest that an accuser had access to God to condemn Christians. It has long been recognised, mainly from the opening chapters of the Book of Job, that Satan performs the role of accuser as far as believers are concerned, and indeed he is called the accuser of the brethren in Revelation 12:10.
It is also possible that the accusations were made in the minds of the believers, and in that second location there was no one to defend them. Each believer has a conscience, which points out his or sins sins and failures to them. If a believer has sinned badly, he can have a very difficult time from his conscience.
As far as both places of accusation were concerned, John told his readers to consider what Jesus was doing for them in heaven. This means that the primary voice they were to listen to with regard to their sins and failings was the voice of their Advocate. While they could not hear literally the voice of the accuser in heaven, they could hear what their consciences were saying. But in their spiritual life they were not to let those voices drown out the voice of their Advocate.
Their Advocate did not base his argument on what could be found in them. He did not mention mitigating circumstances from the past or possible improvements in the future. Instead he constantly pointed to what he himself had done for them when he was here on earth and took their place at Calvary. There he had paid the penalty for their sins long before they had committed them. So whenever the devil accused them the answer was that the penalty had been paid. They had to learn to think the same way with regard to the accusations of their consciences.
This does not mean that they could take personal sin lightly. But they did have to take it realistically. Sinning is inevitable, even with regard to their best activities. What should be their realistic response to it? There should be expressions of repentance and their faith should grasp that their faithful Advocate still represented them and would always do so.