The decision to bring Lisa Maria Zahra's private maths tutor to testify in the compilation of evidence against Erin Tanti this afternoon proved to be controversial, with the defence questioning the relevance of her testimony and harshly criticising her behaviour in court.

Mr Tanti, is accused of murdering 15-year-old Lisa Maria Zahra, assisting her suicide, defiling and participating in sexual acts with her, being in possession of indecent images of the teenager and abusing a position of trust. He was her drama teacher at the time.

Ms Zahra had been found dead at Dingli Cliffs on 19 March, 2013. Mr Tanti was found a few metres away, dazed but only slightly injured.

A number of witnesses testified in today's sitting, but perhaps the most notably testimonies were those of the maths tutor, Marlene Bugeja, and Mr Tanti's friend and business partner James Muscat.

Ms Bugeja had tutored Ms Zahra for nearly two years on a one-to-one basis, but as she described the girl's performance in mathematics, defence counsel Michael Sciriha questioned the point of her testimony.

Parte civile lawyer Joe Giglio then explained that apart from the close contact Ms Bugeja had with Ms Zahra and the conversations that they had, the aim was also to show how a teacher was supposed to behave with students.

The Zahras' lawyers - Giannella de Marco and Steve Tonna Lowell also appeared as parte civile - focused on asking the tutor questions about what Ms Zahra had spoken to her, particularly about her future.

Ms Bugeja noted that Ms Zahra had spoken to her about the upcoming school prom, and that she helped her pick a dress and shoes, among other things.

She said that on their last lesson - on the Sunday before her death - Ms Zahra was very happy, laughing all the time, and had asked to be invited to her wedding and asked when her birthday would be so she could bake cupcakes for her.

"All things pointed to the future, so I cannot understand what happened on Wednesday, 19 March," Ms Bugeja told the court.

Ms Bugeja said that she was set to give Ms Zahra a lesson on the day. She sought to postpone the lesson by a few hours as she was suffering from lactose intolerance symptoms, but could not reach her on her mobile phone.

She said that another student told her about what had happened, but said that she did not believe her, particularly since the first indications were that a suicide had occurred. But she added that when the news was confirmed by a parent, she realised that it was true.

But after observing that "you couldn't help but love Lisa," and how strongly she felt even though she was not related to her when the incident happened, Ms Bugeja's off-the-cuff remarks caused an uproar.

"I cannot understand how this Cliff Dingli," she started, in a reference to a pseudonym Mr Tanti had apparently used during a drama lesson," prompting both Magistrate Audrey Demicoli and Dr Giglio to tell her to stop.

On his part, Dr Sciriha encouraged her to continue, and she went on to ask how Mr Tanti did not feel anything at what happening before Magistrate Demicoli reiterated that she should stop making such remarks. But the lawyer also accused the teacher of acting arrogantly, and even noted that he had never seen such actions in court in thirty years of legal practice.

Ms Bugeja then confirmed that Ms Zahra did reveal that she had a boyfriend, but only mentioned that his name was Erin and that he was short. She said that a boy her age had once accompanied Ms Zahra to her lesson, and that his height led her to assume that he was the one.

During cross-examination, Dr Sciriha once more encouraged her to complete her earlier statement, before asking whether Ms Zahra would reveal any personal matters.

Ms Bugeja said that she did not know of any difficulties Ms Zahra may have been going through, and that she did not seek to check school reports, as she was only interested in her performance in maths.

Tanti lied about Zahra's age, how they met

In his testimony, Mr Muscat explained that he first met Mr Tanti some three years ago, and that at the time of the incident, they were partners in a company which organised stand-up comedy events.

Replying to questions by prosecuting inspector Keith Arnaud, Mr Muscat said that Mr Tanti first revealed that he was seeing someone in November 2013, but would not name her when asked to.

But in January, he invited him and his girlfriend to dinner with him and Lisa, in which he saw her for the first time.

Mr Muscat said that Mr Tanti did mention, at one point, that her father was "powerful," prompting him to quip that he might help with sponsorship, but Mr Tanti ruled this out.

He also testified that Mr Tanti told him that Ms Zahra was "17 going on 18," and did not reveal that he was her teacher. He recalled that Mr Tanti either said that he met her through friends or through the internet.

The last comedy show the two men organised took place last 17 March, two days before Ms Zahra's body was discovered, and on the day, Mr Tanti left early, immediately after his own performance.

But he called him on the evening of the next day, telling him that he appreciated their work and thanking him for being a good friend. Mr Muscat asked him whether he was feeling alright, and Mr Tanti told him that he was, but was feeling a little tired. He added that he did not think much about it.

Asked whether he had noticed any marks on Mr Tanti's body at one point, Mr Muscat noted that he once saw what appeared to be self-inflicted cuts on his forearm, stating that he reacted angrily to them, telling Mr Tanti that if he were to repeat such a thing, it would spell the end of their friendship and comedy project.

But before he did, he clarified that he had been misquoted when, as reported by the media, Insp. Arnaud had testified that he had described Mr Tanti as a sociopath.

What had happened, he said, was that Mr Tanti had spoken to him in confidence and told him that he felt like a sociopath. Mr Muscat said that he did not believe this to be the case, and explained this to Mr Tanti.

He told the court that he may have heard, from other people, that Mr Tanti had a "bad history," but added that he knew him to be a nice guy who was always ready to help him.

Asked to clarify what was meant by bad history, he said a number of people had warned him to "be careful" when he explained that he was involved in a project with Mr Tanti, but would not elaborate. The only exception was someone who claimed that Mr Tanti claimed authorship for what they had written.

But during cross examination by Dr Sciriha, Mr Muscat confirmed that the warnings came from other theatre producers, and Mr Muscat also confirmed that they would have had difficulties with Mr Tanti because of his perfectionism.

"He even had a bad history with me because of his perfectionism," Mr Muscat added.

Mr Muscat also said that Mr Tanti and Ms Zahra appeared to be happy around each other, and that Mr Tanti had told him that he loved her.

Inspector Josric Mifsud also prosecuted, while lawyer Lucio Sciriha also appeared for Mr Tanti.