September is the first month of spring in Zimbabwe. The jacaranda trees that line Harare’s avenues will soon flower into a sea of purple. Last November their blossom formed the backdrop to the people taking to the streets and demanding change. This year, following our democratic election in July, it shall welcome a new era in Zimbabwe.

Winter’s end marked the culmination of months of vigorous campaigning. Candidates were able to cross the country without fear of intimidation to pledge their vision for Zimbabwe like never before.

However, the blossom that signifies the changing seasons does not guarantee the jacaranda trees’ survival. In fact, they are vulnerable species; they must be protected. This election – the freest and fairest in our history – similarly signifies change. But the democracy it heralds must be defended, for it too is fragile.

Sadly, the collective achievement of the election became a prelude to tragedy. Instead of waiting for the vote to be counted, the opposition leadership declared victory in the presidential race. Some of their supporters took to the streets in protest at the yet-to-be-announced result. The situation turned violent. Six lives were lost.

People, rightly, want justice to be served – as do I. However, it is not within the president’s power to impulsively blame or punish those who might appear guilty. What is within my power is the establishment of an independent investigation to ascertain who bears responsibility.

The former president of South Africa, Kgalema Motlanthe, will chair the seven-member team comprised both of Zimbabwean nationals and international experts. They will be sworn in upon my return from China to begin their three months of work.

I shall fully implement the recommendations of this commission. This may not serve political expediency on either side of the divide, but in underpinning justice it serves the people of Zimbabwe’s interests.

A soldier stands guard during the inauguration ceremony of Emmerson Mnangagwa, at the National Sports Stadium in Harare. Photograph: Tsvangirayi Mukwazhi/AP

This is the right action to take in line with the democratic journey we set out on last November. Along this route, I am certain that I have gained false friends whose interests favour the status quo. Yet we cannot let this minority hinder the nation’s progress, nor squander the opportunity that lies before us. Rather we must protect this free and fair election. We must cherish what the people of Zimbabwe have achieved.

I do not say this because it suits my favour. Though the opposition leader fell short of the presidency, through this democratic vote he too has been granted an important mandate: to lead scrutiny of the government’s work in parliament. We must remember that elections are about more than who returns the most votes. For the free and fair Zimbabwe that this election augurs cannot succeed without the opposition holding those in power to account – launching criticism in parliament, not stones in the streets.

This is not to make less of what occurred following the protests. However, for justice to function properly, it must be applied equally to all. The opposition here too have a vital role: they must scrutinise the commission’s work at each step. Although experts drawn from a range of opinion and backgrounds shall sit on the independent commission, we – both government and opposition – must ensure there is no bias through observation and inquiry.

Indeed, the role of opposition leader is critical to democracy’s function. The incoming administration will be weaker if not held to the checks and balances that parliament provides. Were he to renege on this role, it will only sap the nascent democratic culture taking root.

Alleging fraud without substantiating it has a similar effect. In the absence of readily available evidence, it served only to polarise voters. Those who had believed the opposition leader’s claims had to do so in blind faith.

Without such faith, it is difficult to see where this fraud came from. The opposition, however, were fully within their rights to bring their case to court. In fact, it is encouraging to see that the democratic and judicial tools available to them were exercised. In full view of the evidence submitted, the courts found against their claim. Now we must come together to realise what the people of Zimbabwe call out for: prosperity, opportunity and accountability rooted in peace.

So when the jacaranda trees begin to bud, I hope to see the opposition leader criticising the government openly and transparently in parliament – as the people of Zimbabwe deserve. For then the purple blossom that signifies change will also represent health.

• Emmerson Mnangagwa is the president of Zimbabwe